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 A134866 Table read by antidiagonals: T(n,k) = sigma(gcd(n,k)). 4
 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3, 4, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 7, 1, 3, 1, 1, 1, 4, 1, 1, 4, 1, 1, 1, 3, 1, 3, 6, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 4, 7, 1, 12, 1, 7, 4, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 3, 8, 3, 1, 3, 1, 3, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS Previous name was: Triangle, antidiagonals of an array formed by A051731 * A127093 (transform). Row sums give A094471. LINKS Michael De Vlieger, Table of n, a(n) for n = 1..11325 (rows n = 1..150, flattened) FORMULA T(n,k) = A000203(A050873(n,k)). - Michel Marcus, Dec 19 2022 EXAMPLE First few rows of the array: 1, 1, 1, 1, 1, 1, 1, ... 1, 3, 1, 3, 1, 3, 1, ... 1, 1, 4, 1, 1, 4, 1, ... 1, 3, 1, 7, 1, 3, 1, ... 1, 1, 1, 1, 6, 1, 1, ... ... First antidiagonals: 1; 1, 1; 1, 3, 1; 1, 1, 1, 1; 1, 3, 4, 3, 1; 1, 1, 1, 1, 1, 1; 1, 3, 1, 7, 1, 3, 1; 1, 1, 4, 1, 1, 4, 1, 1; 1, 3, 1, 3, 6, 3, 1, 3, 1; ... MATHEMATICA Table[DivisorSigma[1, GCD[#, k]] &[n - k + 1], {n, 13}, {k, n}] // Flatten (* Michael De Vlieger, Dec 19 2022 *) PROG (PARI) T(n, k) = sigma(gcd(n, k)); \\ Michel Marcus, Dec 19 2022 CROSSREFS Cf. A051731, A127093, A094471, A132442. Sequence in context: A031277 A001165 A137420 * A340085 A143261 A204116 Adjacent sequences: A134863 A134864 A134865 * A134867 A134868 A134869 KEYWORD nonn,tabl AUTHOR Gary W. Adamson, Nov 14 2007 EXTENSIONS New name and data corrected by Michel Marcus, Dec 19 2022 STATUS approved

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Last modified September 30 20:07 EDT 2023. Contains 365793 sequences. (Running on oeis4.)