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A342915 a(n) = gcd(1+n, A001615(n)), where A001615 is Dedekind psi, n * Product_{p|n, p prime} (1 + 1/p). 5
1, 3, 4, 1, 6, 1, 8, 3, 2, 1, 12, 1, 14, 3, 8, 1, 18, 1, 20, 3, 2, 1, 24, 1, 2, 3, 4, 1, 30, 1, 32, 3, 2, 1, 12, 1, 38, 3, 8, 1, 42, 1, 44, 9, 2, 1, 48, 1, 2, 3, 4, 1, 54, 1, 8, 3, 2, 1, 60, 1, 62, 3, 32, 1, 6, 1, 68, 3, 2, 1, 72, 1, 74, 3, 4, 1, 6, 1, 80, 9, 2, 1, 84, 1, 2, 3, 8, 1, 90, 1, 4, 3, 2, 1, 24, 1, 98, 3, 4, 1, 102 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..16384

FORMULA

a(n) = gcd(1+n, A001615(n)).

a(n) = (1+n) / A342916(n) = A001615(n) / A342917(n).

PROG

(PARI)

A001615(n) = if(1==n, n, my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1))); \\ After code in A001615

A342915(n) = gcd(1+n, A001615(n));

CROSSREFS

Cf. A001615, A342916, A342917.

Cf. also A049559, A342458.

After n=1 differs from A143771 for the first time at n=44, where a(44) = 9, while A143771(44) = 3.

Sequence in context: A177971 A114156 A339964 * A276433 A343226 A030707

Adjacent sequences:  A342912 A342913 A342914 * A342916 A342917 A342918

KEYWORD

nonn

AUTHOR

Antti Karttunen, Mar 29 2021

STATUS

approved

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Last modified May 6 16:03 EDT 2021. Contains 343586 sequences. (Running on oeis4.)