A123931 a(n) = H(n)*n!/(floor(n/2))! (mod (n+1)), where H(n) = sum{k=1 to n} 1/k, the n-th harmonic number.

0, 1, 0, 3, 0, 5, 0, 2, 3, 4, 0, 0, 0, 6, 9, 0, 0, 0, 0, 0, 18, 10, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 30, 16, 0, 0, 0, 18, 24, 0, 0, 0, 0, 0, 0, 22, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 54, 28, 0, 0, 0, 30, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 36, 0, 0, 0, 0, 0, 0, 0, 40, 0, 0, 0, 42, 51, 0, 0, 0, 0, 0, 3, 46, 0, 0, 0

Offset

0,4

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Mathematica

f[n_]:= Mod[HarmonicNumber[n]n!/Floor[n/2]!, n + 1]; Table[f[n], {n, 0, 100}] (* Ray Chandler, Dec 11 2006 *)

Prog

(PARI) a(n) = (n!*sum(k=1, n, 1/k)/(n\2)!)%(n+1);
vector(100, n, n--; a(n) ) \\ G. C. Greubel, Aug 05 2019
(Sage) [mod(harmonic_number(n)*factorial(n)/factorial(floor(n/2)), n+1) for n in (0..100)] # G. C. Greubel, Aug 05 2019
(GAP)List([0..100], n-> (Factorial(n)*Sum([1..n], k-> 1/k)/Factorial(Int(n/2))) mod (n+1) ); # G. C. Greubel, Aug 05 2019

Crossrefs

Cf. A124078.

Sequence in context: A373023 A340525 A003966 * A058026 A004605 A369700

Adjacent sequences: A123928 A123929 A123930 * A123932 A123933 A123934

Keyword

easy,nonn

Author

Leroy Quet, Nov 28 2006

Extensions

Extended by Ray Chandler, Dec 11 2006

Status

approved