A110374 a(n) = Sum_{composite c <= n} n!/c.

6, 30, 300, 2100, 21840, 236880, 2731680, 30048480, 400498560, 5206481280, 79117758720, 1273944672000, 21690789120000, 368743415040000, 6993068898816000, 132868309077504000, 2779011281958912000, 60792138929313792000, 1388517998616612864000

Offset

4,1

Links

Michael S. Branicky, Table of n, a(n) for n = 4..449

Example

a(8) = 8! * (1/4 + 1/6 + 1/8) = 21840.

Maple

a:=proc(n) local s, i :s:=0: for i from 4 to n do if isprime(i)=false then s:=s+1/i else s:=s: fi od: n!*s; end; seq(a(n), n=4..23); # Emeric Deutsch, Jul 24 2005

Prog

(Python)
from sympy import factorial, isprime, Rational
def a(n): return factorial(n) * sum(Rational(1, c) for c in range(4, n+1) if not isprime(c))
print([a(n) for n in range(4, 23)]) # Michael S. Branicky, Jun 30 2021

Crossrefs

Cf. A110373.

Sequence in context: A295611 A264641 A360824 * A360831 A232978 A359882

Adjacent sequences: A110371 A110372 A110373 * A110375 A110376 A110377

Keyword

easy,nonn

Author

Amarnath Murthy, Jul 24 2005

Extensions

More terms from Emeric Deutsch, Jul 24 2005

a(21) and beyond from Michael S. Branicky, Jun 30 2021

Status

approved