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A126701 a(n) = number of primes <= !n, where !n is subfactorial n. 2
0, 0, 1, 4, 14, 56, 283, 1738, 12457, 102492, 951651, 9830851, 111757480, 1385739200, 18604785172, 268807211509, 4157797131788, 68538901559776, 1199382039260721, 22203590239217092, 433511971123048194, 8902234772796777434, 191798011804919907012 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..23.

Kim Walisch, Fast C++ prime counting function implementation (primecount).

FORMULA

a(n) = A000720(A000166(n)). - Jens Kruse Andersen, Jul 18 2014

EXAMPLE

a(5) = 14, because !5 = 44 and the number of primes up to 44 is 14.

CROSSREFS

Cf. A000720, A000166.

Sequence in context: A073155 A346816 A006212 * A309514 A151884 A002735

Adjacent sequences:  A126698 A126699 A126700 * A126702 A126703 A126704

KEYWORD

hard,nonn

AUTHOR

Shyam Sunder Gupta, Feb 11 2007

EXTENSIONS

a(17)-a(20) from Jens Kruse Andersen, Jul 18 2014

a(21)-a(23) using Kim Walisch's primecount, from Amiram Eldar, Aug 25 2020

STATUS

approved

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Last modified January 20 21:46 EST 2022. Contains 350472 sequences. (Running on oeis4.)