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 A334742 Pascal's spiral: starting with a(1) = 1, proceed in a square spiral, computing each term as the sum of horizontally and vertically adjacent prior terms. 7
 1, 1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 7, 7, 8, 10, 12, 12, 14, 17, 20, 20, 23, 27, 32, 37, 37, 42, 48, 55, 62, 62, 69, 77, 87, 99, 111, 111, 123, 137, 154, 174, 194, 194, 214, 237, 264, 296, 333, 370, 370, 407, 449, 497, 552, 614, 676, 676, 738, 807, 884, 971, 1070 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS This is the square spiral analogy of Pascal's triangle thought of as a table read by antidiagonals. LINKS Peter Kagey, Table of n, a(n) for n = 1..10000 Peter Kagey, Bitmap illustrating the of parity of the first 2^20=1048576 terms. (Even and odd numbers are represented with black and white pixels respectively.) FORMULA a(A033638(n)) = a(A002620(n)) for n > 1. EXAMPLE Spiral begins:   111--99--87--77--69--62                         |    12--12--10---8---7  62     |               |   |    14   2---2---1   7  55     |   |       |   |   |    17   3   1---1   6  48     |   |           |   |    20   3---4---5---5  42     |                   |    20--23--27--32--37--37 a(15) = 10 = 8 + 2, the sum of the cells immediately to the right and below. The term to the left is not included in the sum because it has not yet occurred in the spiral. CROSSREFS Cf. A007318, A141481, A334688. Cf. A180714, A214526, A274640, A278180, A304586, A307834, A334741. x- and y-coordinates are given by A174344 and A274923, respectively. Sequence in context: A024699 A083479 A112231 * A213856 A173329 A241951 Adjacent sequences:  A334739 A334740 A334741 * A334743 A334744 A334745 KEYWORD nonn,nice AUTHOR Alec Jones and Peter Kagey, May 09 2020 STATUS approved

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Last modified June 24 11:45 EDT 2021. Contains 345416 sequences. (Running on oeis4.)