OFFSET
1,1
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
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
The sequence of terms together with their prime indices begins:
221: {6,7}
247: {6,8}
299: {6,9}
403: {6,11}
442: {1,6,7}
494: {1,6,8}
533: {6,13}
598: {1,6,9}
663: {2,6,7}
689: {6,16}
741: {2,6,8}
767: {6,17}
806: {1,6,11}
871: {6,19}
884: {1,1,6,7}
For example, 884 has prime indices {1,1,6,7} with numbers of distinct prime factors (0,0,2,1), which is not weakly increasing, so 884 belongs to the sequence.
MATHEMATICA
Select[Range[1000], !OrderedQ[PrimeNu/@PrimePi/@First/@FactorInteger[#]]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 10 2019
STATUS
approved