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 A279394 Triangle read by rows, T(n,m) = sigma_{n-m}(m) for n >= 1,  m = 1,2, ..., n. 10
 1, 1, 2, 1, 3, 2, 1, 5, 4, 3, 1, 9, 10, 7, 2, 1, 17, 28, 21, 6, 4, 1, 33, 82, 73, 26, 12, 2, 1, 65, 244, 273, 126, 50, 8, 4, 1, 129, 730, 1057, 626, 252, 50, 15, 3, 1, 257, 2188, 4161, 3126, 1394, 344, 85, 13, 4, 1, 513, 6562, 16513, 15626, 8052, 2402, 585, 91, 18, 2, 1, 1025, 19684, 65793, 78126, 47450, 16808, 4369, 757, 130, 12, 6 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS See A109974 (downward antidiagonals) for details and references. sigma_k(n) is the sum of the k-th power of the positive divisors of n. This is the triangle read by rows obtained from the array sigma_k(n) for k >= 0, n >= 1, read by upward antidiagonals. The row sums are A108639. LINKS FORMULA T(n, m) = sigma_{n-m}(m), n >= 1, m = 1..n. EXAMPLE The triangle T(n, m) begins: n\m 1   2    3    4    5    6   7  8  9 10 1:  1 2:  1   2 3:  1   3    2 4:  1   5    4    3 5:  1   9   10    7    2 6:  1  17   28   21    6    4 7:  1  33   82   73   26   12   2 8:  1  65  244  273  126   50   8  4 9:  1 129  730 1057  626  252  50 15  3 10: 1 257 2188 4161 3126 1394 344 85 13  4 ... n = 11: 1 513 6562 16513 15626 8052 2402 585 91 18 2, n = 12: 1 1025 19684 65793 78126 47450 16808 4369 757 130 12 6. ... MAPLE T := (n, k) -> numtheory:-sigma[n-k](k): seq(seq(T(n, k), k=1..n), n=1..12); # Peter Luschny, Jan 07 2017 MATHEMATICA Table[DivisorSigma[k, #] &[n - k + 1], {n, 0, 11}, {k, n, 0, -1}] (* Michael De Vlieger, Jan 09 2017 *) CROSSREFS Cf. A109974, A108639. Sequence in context: A131344 A129262 A322263 * A308509 A280514 A246105 Adjacent sequences:  A279391 A279392 A279393 * A279395 A279396 A279397 KEYWORD nonn,tabl,easy AUTHOR Wolfdieter Lang, Jan 07 2017 STATUS approved

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Last modified May 26 13:39 EDT 2020. Contains 334626 sequences. (Running on oeis4.)