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 A334836 a(n) = A334769(k) where k is the first position of n in A334796. 4
 151, 543, 10707, 33151, 345283, 2213663, 33629695, 134297599, 1109207903, 8657682303, 73283989519 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS This sequence indexes the smallest number m = A334769(k) that, when expressed in binary b(k), generates a rotationally symmetrical XOR-triangle (RST) that features a central zero-triangle (CZT) with frame width n. A "frame width" is the number of iterations j required to generate the first run of zeros in a CZT of an RST. Let L = A070939(m) for m in A334769. For RSTs, j > 1, since a solid run of L 1s given a recursive XOR function applied to each pair of adjacent bits, would give rise to a solid run of (L - 1) zeros in the next iteration, and every iteration thereafter consists of zeros. Therefore m = (2(L - 1) - 1) is not rotationally symmetrical except when L = 1. Sequence A334556 lists numbers m that produce RSTs; A334769 those RSTs that feature CZTs. Sequence A334796 renders the frame widths j for numbers in A334769. For n = 7, A070939(a(n)) > 3(7) + 1 = 22, but is likely much larger, given a(6). a(7) is likely a number with more than 40 bits. LINKS Michael De Vlieger, Diagram montage showing XOR-triangles of each a(n) for 2 <= n <= 12. Michael De Vlieger, Aspects of XOR-triangles T(a(n)) EXAMPLE a(2) = 151; Rotationally symmetrical XOR-triangle generated by 151, replacing 0s with "." for clarity, showing 2 bits to reach the central zero triangle of side length s = 2:   1 . . 1 . 1 1 1    1 . 1 1 1 . .     1 1 . . 1 .      . 1 . 1 1       1 1 1 .        . . 1         . 1          1 a(3) = 543; RST generated by 543, showing 3 bits to reach the CZT of side length s = 1 = A334770(3):   1 . . . . 1 1 1 1 1    1 . . . 1 . . . .     1 . . 1 1 . . .      1 . 1 . 1 . .       1 1 1 1 1 .        . . . . 1         . . . 1          . . 1           . 1            1 CROSSREFS Cf. A016777, A070939, A334556, A334769, A334796. Sequence in context: A164622 A176138 A139640 * A130870 A211555 A143012 Adjacent sequences:  A334833 A334834 A334835 * A334837 A334838 A334839 KEYWORD nonn,more AUTHOR Michael De Vlieger, May 13 2020 STATUS approved

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Last modified September 29 21:59 EDT 2020. Contains 337432 sequences. (Running on oeis4.)