A318992 - OEIS

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A318992

Numbers whose consecutive prime indices are not all divisible.

15, 30, 33, 35, 45, 51, 55, 60, 66, 69, 70, 75, 77, 85, 90, 91, 93, 95, 99, 102, 105, 110, 119, 120, 123, 132, 135, 138, 140, 141, 143, 145, 150, 153, 154, 155, 161, 165, 170, 175, 177, 180, 182, 186, 187, 190, 195, 198, 201, 203, 204, 205, 207, 209, 210, 215

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..10000

EXAMPLE

The sequence of partitions whose Heinz numbers belong to the sequence begins: (3,2), (3,2,1), (5,2), (4,3), (3,2,2), (7,2), (5,3), (3,2,1,1), (5,2,1), (9,2), (4,3,1), (3,3,2), (5,4), (7,3), (3,2,2,1), (6,4), (11,2), (8,3), (5,2,2).

MATHEMATICA

Select[Range[100], !Or[#==1, PrimePowerQ[#], Divisible@@Reverse[PrimePi/@FactorInteger[#][[All, 1]]]]&]

PROG

(PARI) ok(n)={my(v=apply(primepi, factor(n)[, 1])); for(i=2, #v, if(v[i]%v[i-1], return(1))); 0} \\ Andrew Howroyd, Oct 26 2018

CROSSREFS

Cf. A000040, A001221, A001222, A008480, A289509, A300912, A318990, A318991, A318993.

Sequence in context: A067400 A115801 A343343 * A343337 A347455 A324970

Adjacent sequences: A318989 A318990 A318991 * A318993 A318994 A318995

KEYWORD

nonn

AUTHOR

Gus Wiseman, Sep 06 2018

STATUS

approved