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A226196
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Triangular numbers which are an average of four consecutive primes.
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2
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15, 55, 105, 120, 253, 595, 1225, 1485, 2080, 2211, 3321, 4371, 5460, 6786, 7381, 7503, 10731, 11935, 12246, 16290, 18915, 24531, 24753, 27966, 36585, 44850, 51360, 55278, 55945, 56953, 60031, 64980, 68265, 69006, 70125, 75078, 86736, 87153, 92235, 94830, 98790, 111628
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OFFSET
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1,1
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LINKS
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FORMULA
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MAPLE
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A000217inv:=proc(n)
local t1;
t1:=floor(sqrt(2*n));
if n = t1*(t1+1)/2 then
return t1 ;
else
return -1;
end if;
end proc:
for n from 1 to 90000 do
if type(s, 'integer') then
tr := A000217inv(s) ;
if tr >= 0 then
printf("%d, ", s) ;
end if;
end if;
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MATHEMATICA
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Select[Mean/@Partition[Prime[Range[20000]], 4, 1], OddQ[Sqrt[8#+1]]&] (* Harvey P. Dale, Dec 18 2015 *)
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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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