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A328219 LCM of the prime indices of n, all plus 1. 7
1, 2, 3, 2, 4, 6, 5, 2, 3, 4, 6, 6, 7, 10, 12, 2, 8, 6, 9, 4, 15, 6, 10, 6, 4, 14, 3, 10, 11, 12, 12, 2, 6, 8, 20, 6, 13, 18, 21, 4, 14, 30, 15, 6, 12, 10, 16, 6, 5, 4, 24, 14, 17, 6, 12, 10, 9, 22, 18, 12, 19, 12, 15, 2, 28, 6, 20, 8, 30, 20, 21, 6, 22, 26 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

LINKS

Table of n, a(n) for n=1..74.

FORMULA

a(n) = A290103(A003961(n)).

If n = A000040(i_1) * ... * A000040(i_k), then a(n) = lcm(1+i_1,...,1+i_k).

MATHEMATICA

Table[If[n==1, 1, LCM@@(PrimePi/@First/@FactorInteger[n]+1)], {n, 100}]

PROG

(PARI)

A003961(n) = my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); \\ From A003961

A290103(n) = lcm(apply(p->primepi(p), factor(n)[, 1]));

A328219(n) = A290103(A003961(n)); \\ Antti Karttunen, Oct 18 2019

CROSSREFS

Sorted positions of first appearances are A328451.

LCM of prime indices is A290103.

LCM of prime indices minus 1 is A328456.

GCD of prime indices plus 1 is A328169.

Partitions whose parts plus 1 are relatively prime are A318980.

Numbers whose prime indices plus 1 are relatively prime are A318981,

Cf. A003961, A056239, A112798, A258409, A289508, A289509, A328167, A328168.

Sequence in context: A006047 A285712 A062068 * A328879 A130542 A128502

Adjacent sequences:  A328216 A328217 A328218 * A328220 A328221 A328222

KEYWORD

nonn

AUTHOR

Gus Wiseman, Oct 16 2019

STATUS

approved

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Last modified March 8 00:38 EST 2021. Contains 341934 sequences. (Running on oeis4.)