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A318981
Numbers whose prime indices plus 1 are relatively prime.
8
1, 6, 12, 14, 15, 18, 21, 24, 26, 28, 30, 35, 36, 38, 39, 42, 45, 48, 51, 52, 54, 56, 58, 60, 63, 65, 66, 69, 70, 72, 74, 75, 76, 77, 78, 84, 86, 87, 90, 91, 95, 96, 98, 102, 104, 105, 106, 108, 111, 112, 114, 116, 117, 119, 120, 122, 123, 126, 130, 132, 133
OFFSET
1,2
COMMENTS
A prime index of n is a number m such that prime(m) divides n.
EXAMPLE
The sequence of integer partitions whose Heinz numbers are in the sequence begins: (), (21), (211), (41), (32), (221), (42), (2111), (61), (411), (321), (43), (2211), (81), (62), (421), (322), (21111).
MATHEMATICA
Select[Range[100], GCD@@(PrimePi/@FactorInteger[#][[All, 1]]+1)==1&]
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 06 2018
STATUS
approved