A328456 LCM of the prime indices of 2n + 1, all minus 1; a(0) = 0.

0, 1, 2, 3, 1, 4, 5, 2, 6, 7, 3, 8, 2, 1, 9, 10, 4, 6, 11, 5, 12, 13, 2, 14, 3, 6, 15, 4, 7, 16, 17, 3, 10, 18, 8, 19, 20, 2, 12, 21, 1, 22, 6, 9, 23, 15, 10, 14, 24, 4, 25, 26, 6, 27, 28, 11, 29, 8, 5, 6, 4, 12, 2, 30, 13, 31, 21, 2, 32, 33, 14, 20, 18, 3, 34

Offset

0,3

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=0..74.

Example

The prime indices of 2 * 17 + 1 = 35, all minus 1, are {2,3}, with LCM 6, so a(17) = 6.

Mathematica

Table[If[n==1, 0, LCM@@(PrimePi/@First/@FactorInteger[n]-1)], {n, 1, 100, 2}]

Crossrefs

Positions of records (first appearances) are A006005.

The GCD of the prime indices of n, all minus 1, is A328167(n).

The LCM of the prime indices of n, all plus 1, is A328219(n).

Partitions whose parts minus 1 are relatively prime are A328170.

Numbers whose prime indices minus 1 are relatively prime are A328168.

Cf. A056239, A112798, A258409, A289508, A289509, A290103, A318981, A328169, A328451.

Sequence in context: A137671 A256946 A285715 * A253887 A026370 A078446

Adjacent sequences: A328453 A328454 A328455 * A328457 A328458 A328459

Keyword

nonn

Author

Gus Wiseman, Oct 17 2019

Status

approved