A290599 Number of numbers from 1 to A002808(n) - 1 that are non-coprime to A002808(n).

1, 3, 3, 2, 5, 7, 7, 6, 7, 11, 11, 8, 11, 15, 4, 13, 8, 15, 21, 15, 12, 17, 10, 23, 19, 14, 23, 29, 23, 20, 23, 31, 6, 29, 18, 27, 35, 14, 31, 20, 29, 43, 31, 26, 31, 16, 45, 35, 24, 45, 47, 37, 34, 39, 16, 53, 47, 26, 41, 59, 20, 43, 30, 47, 65, 18, 47, 32, 47, 22, 63, 55, 38, 59

Offset: 1

Author

Wolfdieter Lang, Aug 30 2017

Keywords

• nonn

Comments

a(n) is the number of positive numbers k < A002808(n) with gcd(A002808(n), k) not 1.

a(n) gives the row length of the irregular triangle A290600.

Examples

			a(4) = 2 because A002808(4) = 9, with the two non-coprime positive numbers smaller than 9, namely 3 and 6. See row n = 4 of A290600.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A002808, A016035, A290600.

Programs

PARI

[k-1-eulerphi(k) | k<-[2..100], !isprime(k)] \\ Andrew Howroyd, Apr 26 2020

Formula

a(n) = A016035(A002808(n)). - Andrew Howroyd, Apr 26 2020

Extensions

Terms a(51) and beyond from Andrew Howroyd, Apr 26 2020