login
a(n) is the least integer that can be expressed as the difference of two heptagonal numbers in exactly n ways.
4

%I #7 Apr 13 2020 08:02:14

%S 1,81,468,1911,6237,11781,21021,51051,81081,121737,261261,318087,

%T 513513,671517,1145529,1072071,1582581,1378377,3216213,2513511,

%U 4135131,4700619,5666661,11792781,8729721,11810799,15444891,19270251,15162147,24657633,28945917,26189163

%N a(n) is the least integer that can be expressed as the difference of two heptagonal numbers in exactly n ways.

%C The least integer that can be expressed as the sum of one or more consecutive numbers congruent to 1 mod 5 in exactly n ways.

%C Index of first occurrence of n in A333817.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HeptagonalNumber.html">Heptagonal Number</a>

%H <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>

%Y Cf. A000566, A016861, A038547, A068314, A333817, A334011, A334034, A334035, A334037.

%K nonn

%O 1,2

%A _Ilya Gutkovskiy_, Apr 12 2020

%E More terms from _Jinyuan Wang_, Apr 13 2020