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A290599
Number of numbers from 1 to A002808(n) - 1 that are non-coprime to A002808(n).
4
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
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
KEYWORD
nonn
AUTHOR
Wolfdieter Lang, Aug 30 2017
EXTENSIONS
Terms a(51) and beyond from Andrew Howroyd, Apr 26 2020
STATUS
approved