A022267 - OEIS

Write 0, 1, 2, 3, 4, ... in a triangular spiral; then a(n) is the sequence found by reading the line from 0 in the direction 0, 5, ... . The spiral begins:

.

15

/ \

16 14

/ \

17 3 13

/ / \ \

18 4 2 12

/ / \ \

19 5 0---1 11

/ / \

20 6---7---8---9--10

.

(End)

a(n) is the sum of n consecutive integers starting from 4*n+1: (5), (9+10), (13+14+15), ... - Klaus Purath, Jul 07 2020

a(n) with n>0 are the numbers with the periodic length 3 in the Bulgarian and Mancala solitaire. - Paul Weisenhorn, Jan 29 2022