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

1,2

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.

Links

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

Formula

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

Example

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.

Prog

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

Crossrefs

Cf. A002808, A016035, A290600.

Sequence in context: A265751 A143050 A214919 * A070163 A083343 A360736

Adjacent sequences: A290596 A290597 A290598 * A290600 A290601 A290602

Keyword

nonn

Author

Wolfdieter Lang, Aug 30 2017

Extensions

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

Status

approved