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A173421 Triangular numbers which are sums of 5 consecutive primes. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 27 22:27 EDT 2022. Contains 354899 sequences. (Running on oeis4.)