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 A191910 Triangle read by rows: T(n,n)=n; T(n,k) = k-1 if k divides n and k < n, otherwise -1. 2
 1, 0, 2, 0, -1, 3, 0, 1, -1, 4, 0, -1, -1, -1, 5, 0, 1, 2, -1, -1, 6, 0, -1, -1, -1, -1, -1, 7, 0, 1, -1, 3, -1, -1, -1, 8, 0, -1, 2, -1, -1, -1, -1, -1, 9, 0, 1, -1, -1, 4, -1, -1, -1, -1, 10, 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, 11, 0, 1, 2, 3, -1, 5, -1, -1, -1, -1, -1, 12, 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 13 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The double limit lim_{k->infinity} (lim_{m->infinity} (Sum_{n=1..m} T(n,k)/n)) equals the Euler-Mascheroni constant A001620. LINKS Table of n, a(n) for n=1..91. EXAMPLE Triangle starts: 1; 0, 2; 0, -1, 3; 0, 1, -1, 4; 0, -1, -1, -1, 5; 0, 1, 2, -1, -1, 6; 0, -1, -1, -1, -1, -1, 7; 0, 1, -1, 3, -1, -1, -1, 8; 0, -1, 2, -1, -1, -1, -1, -1, 9; MAPLE A191910 := proc(n, k) if n = k then n; elif modp(n, k) = 0 then k-1 ; else -1; end if; end proc: seq(seq(A191910(n, k), k=1..n), n=1..20); # R. J. Mathar, Aug 03 2011 MATHEMATICA Clear[t]; nn = 13; t[n_, k_] := t[n, k] = If[n <= k, 1, 0] - If[Mod[n, k] == 0, (1 - k), 1]; Flatten[Table[Table[t[n, k], {k, 1, n}], {n, 1, nn}]] (*The double limit for gamma:*) Clear[t]; nn = 1000; kk = 60; t[n_, k_] := t[n, k] = If[n <= k, 1, 0] - If[Mod[n, k] == 0, (1 - k), 1]; a = Table[t[n, kk], {n, 1, nn}]; MatrixForm[a]; b = Range[nn]; gamma = N[Total[a/b]] CROSSREFS Cf. A001620, A191907. Sequence in context: A141097 A278045 A096335 * A129503 A225682 A144185 Adjacent sequences: A191907 A191908 A191909 * A191911 A191912 A191913 KEYWORD sign,tabl,easy AUTHOR Mats Granvik, Jun 19 2011 STATUS approved

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Last modified September 11 05:49 EDT 2024. Contains 375814 sequences. (Running on oeis4.)