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

Author

Gus Wiseman, Oct 17 2019

Keywords

• nonn

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.

Examples

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

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.

Programs

Mathematica

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