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 A128177 A128174 * A004736 as infinite lower triangular matrices. 0
 1, 2, 1, 4, 2, 1, 6, 4, 2, 1, 9, 6, 4, 2, 1, 12, 9, 6, 4, 2, 1, 16, 12, 9, 6, 4, 2, 1, 20, 16, 12, 9, 6, 4, 2, 1, 25, 20, 16, 12, 9, 6, 4, 2, 1, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1, 36, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1, 42, 36, 30, 25, 20, 16, 12, 9, 6, 4, 2, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS n-th row has n nonzero terms of A002620: (1, 2, 4, 6, 9, 12, 16, ...) in reverse. Row sums = A002623: (1, 3, 7, 13, 22, 34, 50, ...). LINKS EXAMPLE First few rows of the triangle are: 1; 2, 1; 4, 2, 1; 6, 4, 2, 1; 9, 6, 4, 2, 1; 12, 9, 6, 4, 2, 1; ... PROG (PARI) lista(nn) = {t128174 = matrix(nn, nn, n, k, (k<=n)*(1+(-1)^(n-k))/2); t004736 = matrix(nn, nn, n, k, (k<=n)*(n - k + 1)); t128177 = t128174*t004736; for (n = 1, nn, for (k = 1, n, print1(t128177[n, k], ", "); ); ); } \\ Michel Marcus, Feb 11 2014 CROSSREFS Cf. A128174, A004736, A002623, A002620. Sequence in context: A347069 A325309 A211956 * A087738 A133113 A124840 Adjacent sequences:  A128174 A128175 A128176 * A128178 A128179 A128180 KEYWORD nonn,tabl AUTHOR Gary W. Adamson, Feb 17 2007 EXTENSIONS Partially edited and more terms from Michel Marcus, Feb 11 2014 STATUS approved

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Last modified January 25 12:40 EST 2022. Contains 350572 sequences. (Running on oeis4.)