S000791


Prime numbers that are the sum of consecutive pentagonal numbers.

5, 17, 457, 617, 1009, 1777, 2081, 3137, 4409, 5897, 9521, 11657, 14009, 24481, 25577, 29009, 39217, 43441, 47881, 49409, 62497, 67801, 75209, 81017, 85009, 87041, 93281, 97561, 104161, 110977, 120401, 132721, 135257, 140401, 159161, 182041, 194057, 203321

1

S000791

The only prime pentagonal number is 5, the first term. Other terms are the sum of 2 consecutive pentagonal numbers.

T. D. Noe, Plot of 1000 terms

T. D. Noe, Table of 1000 terms

Wikipedia, Polygonal number

(Mma) nn = 400; f = 5; s = Table[k ((f - 2) k - (f - 4))/2, {k, nn}]; t = Table[Select[Plus @@@ Partition[s, n, 1], PrimeQ], {n, 6}]; mx = Min[Select[Max /@ Rest[t], # > 0 &]]; Select[Union[Flatten[t]], # <= mx &]

Cf. A163251 (squares), S000790-S000799.

nonn

T. D. Noe, Dec 11 2015

© Tony D Noe 2014-2015