A173421 Triangular numbers which are sums of 5 consecutive primes.

28, 351, 1891, 4851, 7381, 9453, 15931, 26565, 31125, 68635, 90951, 110685, 130305, 140185, 218791, 224785, 240471, 243253, 309291, 341551, 466095, 497503, 780625, 889111, 899811, 1122751, 1188111, 1214461, 1269621, 1334161, 1408681, 1595791

Offset

1,1

Links

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Example

28 = 2 + 3 + 5 + 7 + 11.

Mathematica

f[n_]:=Prime[n]+Prime[n+1]+Prime[n+2]+Prime[n+3]+Prime[n+4]; Select[Table[f[n], {n, 9!}], IntegerQ[Sqrt[1+8# ]]&]
Select[Total/@Partition[Prime[Range[50000]], 5, 1], OddQ[Sqrt[1+8#]]&] (* Harvey P. Dale, Feb 08 2020 *)

Prog

(Magma) [ t: n in [1..28000] | IsSquare(8*t+1) where t is &+[NthPrime(n+s): s in [0..4]] ]; // Bruno Berselli, Apr 28 2011

Crossrefs

Cf. A000040, A000217, A111163, A167788, A173420.

Sequence in context: A010833 A022720 A272174 * A085744 A163719 A138452

Adjacent sequences: A173418 A173419 A173420 * A173422 A173423 A173424

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 18 2010

Status

approved