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 A128489 Triangle read by rows: A000012 * A126988 as infinite lower triangular matrices. 2
 1, 3, 1, 6, 1, 1, 10, 3, 1, 1, 15, 3, 1, 1, 1, 21, 6, 3, 1, 1, 1, 28, 6, 3, 1, 1, 1, 1, 36, 10, 3, 3, 1, 1, 1, 1, 45, 10, 6, 3, 1, 1, 1, 1, 1, 55, 15, 6, 3, 3, 1, 1, 1, 1, 1, 66, 15, 6, 3, 3, 1, 1, 1, 1, 1, 1, 78, 21, 10, 6, 3, 3, 1, 1, 1, 1, 1, 1, 91, 21, 10, 6, 3, 3, 1, 1, 1, 1, 1, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row sums = A024916: (1, 4, 8, 15, 21, 33, ...). LINKS Table of n, a(n) for n=1..91. FORMULA By columns, k=1,2,3,...; k repeated terms of the triangular series, (1, 3, 6, 10, ...) in the k-th column. EXAMPLE First few rows of the triangle: 1; 3, 1; 6, 1, 1; 10, 3, 1, 1; 15, 3, 1, 1, 1; 21, 6, 3, 1, 1, 1; 28, 6, 3, 1, 1, 1, 1; 36, 10, 3, 3, 1, 1, 1, 1; 45, 10, 6, 3, 1, 1, 1, 1, 1; ... CROSSREFS Cf. A000012, A000217, A024916, A126988. Sequence in context: A099512 A127096 A130541 * A034839 A089732 A158905 Adjacent sequences: A128486 A128487 A128488 * A128490 A128491 A128492 KEYWORD nonn,tabl AUTHOR Gary W. Adamson, Mar 04 2007 EXTENSIONS a(11) = 1 inserted and more terms from Georg Fischer, May 29 2023 STATUS approved

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Last modified July 13 15:08 EDT 2024. Contains 374284 sequences. (Running on oeis4.)