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A084993
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Total number of parts in all partitions of n into prime parts.
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13
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0, 1, 1, 2, 3, 5, 6, 9, 12, 16, 20, 27, 33, 42, 53, 64, 80, 96, 117, 141, 169, 201, 239, 282, 333, 390, 456, 532, 617, 715, 826, 951, 1094, 1253, 1435, 1636, 1864, 2119, 2404, 2723, 3078, 3473, 3915, 4403, 4947, 5549, 6215, 6952, 7767, 8665, 9656, 10748
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OFFSET
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1,4
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LINKS
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FORMULA
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G.f.: sum(x^p(j)/(1-x^p(j)),j=1..infinity)/product(1-x^p(j), j=1..infinity), where p(j) is the j-th prime. - Emeric Deutsch, Mar 07 2006
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EXAMPLE
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Partitions of 9 into primes are 2+2+2+3=3+3+3=2+2+5=2+7; thus a(9)=4+3+3+2=12.
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MAPLE
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g:=sum(x^ithprime(j)/(1-x^ithprime(j)), j=1..20)/product(1-x^ithprime(j), j=1..20): gser:=series(g, x=0, 60): seq(coeff(gser, x^n), n=1..57); # Emeric Deutsch, Mar 07 2006
# second Maple program:
with(numtheory):
b:= proc(n, i) option remember; local g;
if n=0 then [1, 0]
elif i<1 then [0, 0]
elif i=1 then `if`(irem(n, 2)=0, [1, n/2], [0, 0])
else g:= `if`(ithprime(i)>n, [0$2], b(n-ithprime(i), i));
b(n, i-1) +g +[0, g[1]]
fi
end:
a:= n-> b(n, pi(n))[2]:
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MATHEMATICA
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nn=40; a=Product[1/(1-y x^i), {i, Table[Prime[n], {n, 1, nn}]}]; Drop[CoefficientList[Series[D[a, y]/.y->1, {x, 0, nn}], x], 1] (* Geoffrey Critzer, Oct 30 2012 *)
b[n_, i_] := b[n, i] = Module[{g}, Which[n == 0, {1, 0}, i < 1, {0, 0}, i == 1, If[EvenQ[n], {1, n/2}, {0, 0}], True, g = If[Prime[i] > n, {0, 0}, b[n - Prime[i], i]]; b[n, i - 1] + g + {0, g[[1]]}]];
a[n_] := b[n, PrimePi[n]][[2]];
Table[Length[Flatten[Select[IntegerPartitions[n], AllTrue[#, PrimeQ]&]]], {n, 60}] (* Harvey P. Dale, Jul 11 2023 *)
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PROG
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(PARI)
sumparts(n, pred)={sum(k=1, n, 1/(1-pred(k)*x^k) - 1 + O(x*x^n))/prod(k=1, n, 1-pred(k)*x^k + O(x*x^n))}
{my(n=60); Vec(sumparts(n, isprime), -n)} \\ Andrew Howroyd, Dec 28 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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