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A328456 LCM of the prime indices of 2n + 1, all minus 1; a(0) = 0. 2
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 (list; graph; refs; listen; history; text; internal format)
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
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.
Sequence in context: A137671 A256946 A285715 * A253887 A026370 A078446
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 17 2019
STATUS
approved

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Last modified July 23 19:43 EDT 2024. Contains 374553 sequences. (Running on oeis4.)