A319184 - OEIS

A319184

Numbers that are sums of consecutive pentagonal numbers.

0, 1, 5, 6, 12, 17, 18, 22, 34, 35, 39, 40, 51, 57, 69, 70, 74, 75, 86, 92, 108, 117, 120, 121, 125, 126, 145, 156, 162, 176, 178, 190, 195, 196, 209, 210, 213, 247, 248, 262, 270, 279, 282, 287, 288, 321, 330, 354, 365, 376, 386, 387, 399, 404, 405, 424, 425, 438, 457, 475

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OFFSET

1,3

LINKS

Table of n, a(n) for n=1..60.

Eric Weisstein's World of Mathematics, Pentagonal Number

MATHEMATICA

anmax = 1000; nmax = Floor[Sqrt[2*anmax/3]] + 1; Select[Union[Flatten[Table[Sum[k*(3*k-1)/2, {k, i, j}], {i, 0, nmax}, {j, i, nmax}]]], # <= anmax &] (* Vaclav Kotesovec, Dec 21 2018 *)

CROSSREFS

Cf. A000326, A002411, A034705, A034706, A319185, A322636, A322637.

Sequence in context: A032707 A240756 A127306 * A231959 A362948 A168145

Adjacent sequences: A319181 A319182 A319183 * A319185 A319186 A319187

KEYWORD

nonn,changed

AUTHOR

Ilya Gutkovskiy, Dec 21 2018

STATUS

approved