1,2

Denominator of SUM[i=1..n]n!/(n^2) is A121566. The floor of the ratios, 1, 2, 3, 8, 28, 131, 761, 5241, 41529, 371420, 3697820, 40544097, 485331297, 6297217377, 88026865377, 1318779211730, 21079191883730, 358046229027309, 6440301249468909 is not yet in OEIS. See also A070826 One half of product of first n primes A000040 = {1, 3, 15, 105, 1155, 15015, 255255, 4849845, ...}. See also A056839 Square-free part of LCM[1,...,n] = {1, 2, 6, 3, 15, 15, 105, 210, 70, 70, 770, 770, 10010, 10010, 10010, 5005, 85085, 85085...}.

Numerator of SUM[i=1..n] A000142(i)/A000290(i).

a(1) = 1/1 = 1.

a(2) = 3/2 = 1.5.

a(3) = 13/6 = 2.16666666667.

a(4) = 11/3 = 3.66666666667.

a(5) = 127/15 = 8.46666666667.

Cf. A000040, A000142, A000290, A070826, A121566.

Sequence in context: A085416 A107802 A066674 this_sequence A107733 A054767 A137947

Adjacent sequences: A121562 A121563 A121564 this_sequence A121566 A121567 A121568

easy,frac,nonn

Jonathan Vos Post (jvospost2(AT)yahoo.com), Aug 07 2006