This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A321740 #14 Sep 19 2020 03:41:57 %S A321740 1,0,1,0,0,1,1,0,0,1,0,1,0,0,1,0,0,1,1,0,1,0,0,0,1,0,1,1,0,0,0,0,1,0, %T A321740 0,2,1,0,0,0,0,1,0,0,1,1,0,1,0,0,0,1,0,0,1,0,1,0,0,1,1,0,1,0,0,1,0,0, %U A321740 1,0,0,0,1,0,2,0,0,1,0,0,0,1,0,0,0,0,1,1,0,1,2,0 %N A321740 Number of representations of n as a truncated triangular number. %C A321740 A truncated triangular number is a figurate number, the number of dots in a hexagonal diagram where the side lengths alternate between two values. This sequence gives the number of ways that a number can be represented in this form. %C A321740 In a sense this sequence is a hexagonal analog of A038548, which asks the same question for rectangular numbers, and A001227 for trapezoidal numbers. %C A321740 These sequences usually turn out to count divisors of a particular form, of a number simply related to n, but such a formulation is not yet known in this case. %C A321740 Indices for which this sequence is nonzero are at A008912; this sequence is 2 or greater at the indices given in A319602. %e A321740 a(36) = 2 because 36 can be achieved with hexagons of sides (1,9,1,9,1,9) and (3,5,3,5,3,5). %Y A321740 Cf. A008912, A008867, A319602, A322491, A322492. %K A321740 nonn %O A321740 1,36 %A A321740 _Allan C. Wechsler_, Nov 17 2018 %E A321740 More terms from _Hugo Pfoertner_, Sep 18 2020