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A210110
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Primes p such that 2p*(p+1) is the sum of 2 successive primes.
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1
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2, 3, 5, 7, 23, 29, 41, 59, 79, 89, 101, 131, 139, 151, 197, 229, 317, 337, 347, 389, 397, 421, 479, 631, 743, 761, 821, 829, 953, 977, 1033, 1193, 1279, 1451, 1697, 1747, 1787, 1789, 1879, 1997, 1999, 2017, 2099, 2213, 2237, 2347, 2411, 2477, 2579, 2621, 2663
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2 is in the sequence because 2*2*(2+1) = 5+7 = 12.
3 is in the sequence because 2*3*(3+1) = 11+13 = 24.
5 is in the sequence because 2*5*(5+1) = 29+31 = 60.
7 is in the sequence because 2*7*(7+1) = 53+59 = 112.
23 is in the sequence because 2*23*(23+1) = 547+557 = 1104.
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MAPLE
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a:= proc(n) option remember; local p, t;
p:= `if`(n=1, 1, a(n-1));
do p:= nextprime(p);
t:= p*(p+1);
if prevprime(t)+nextprime(t)=2*t then return p fi
od
end:
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MATHEMATICA
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a[n_] := a[n] = Module[{p, t}, p = If[n==1, 1, a[n-1]]; While[True, p = NextPrime[p]; t = p(p+1); If[NextPrime[t, -1] + NextPrime[t]==2t, Return[p]]]];
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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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