OFFSET
1,2
COMMENTS
A prime index of n is a number m such that prime(m) divides n.
The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..10000
EXAMPLE
The sequence of all dividing partitions (columns) begins:
1 2 1 3 2 4 1 2 3 5 2 6 4 1 7 2 8 3 4 5 9 2 3 6 2 4
1 1 1 2 1 1 1 1 2 1 2 1 1 3 1 2 1
1 1 1 1 1 1 2 1
1 1
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(0))); 1} \\ Andrew Howroyd, Oct 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 06 2018
STATUS
approved