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 A350632 a(n) is the total number of ON cells at stage n of a cellular automaton where cells are turned ON when they have one or two neighbors ON (see Comments for precise definition). 4
 0, 1, 9, 21, 45, 57, 85, 121, 177, 189, 217, 253, 329, 373, 465, 557, 721, 737, 765, 801, 877, 921, 1013, 1105, 1301, 1377, 1485, 1601, 1805, 1985, 2221, 2449, 2873, 2909, 2937, 2973, 3049, 3093, 3185, 3277, 3473, 3549, 3657, 3773, 3977, 4157, 4393, 4621, 5113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS On the infinite square grid, start with all cells OFF. Turn a single cell to the ON state. At each subsequent step, each cell with exactly one or two neighbors ON is turned ON, and everything that is already ON remains ON. Here "neighbor" refers to the eight adjacent and diagonally adjacent cells in the Moore neighborhood. LINKS Rémy Sigrist, Log periodic coloring of the structure at stage 512 Rémy Sigrist, C++ program for A350632 EXAMPLE The first 5 generations can be depicted as follows: . . . . . . . . . . . . 5 5 . . . . . 5 5 . . 5 4 4 4 4 4 4 4 5 . . . 4 3 3 . 3 3 4 . . . . 4 3 2 2 2 3 4 . . . . 4 . 2 1 2 . 4 . . . . 4 3 2 2 2 3 4 . . . . 4 3 3 . 3 3 4 . . . 5 4 4 4 4 4 4 4 5 . . 5 5 . . . . . 5 5 . . . . . . . . . . . . - so a(0) = 0, a(1) = 0 + 1 = 1, a(2) = 1 + 8 = 9, a(3) = 9 + 12 = 21, a(4) = 21 + 24 = 45, a(5) = 45 + 12 = 57. PROG (C++) See Links section. CROSSREFS Cf. A147562, A151725, A160414, A256530, A350633, A350639. Sequence in context: A110680 A163205 A154862 * A020137 A231570 A020190 Adjacent sequences: A350629 A350630 A350631 * A350633 A350634 A350635 KEYWORD nonn AUTHOR Rémy Sigrist, Jan 08 2022 STATUS approved

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Last modified March 30 14:15 EDT 2023. Contains 361622 sequences. (Running on oeis4.)