OFFSET
1,1
COMMENTS
A number's prime signature (row n of A124010) is the sequence of positive exponents in its prime factorization.
Also numbers whose multiset of prime factors is not weakly alternating, where we define a sequence to be weakly alternating if it is alternately weakly increasing and weakly decreasing, starting with either. This sequence looks at the somewhat degenerate case where no strict decreases are allowed.
EXAMPLE
The terms and their prime indices begin:
30: {1,2,3}
42: {1,2,4}
60: {1,1,2,3}
66: {1,2,5}
70: {1,3,4}
78: {1,2,6}
84: {1,1,2,4}
102: {1,2,7}
105: {2,3,4}
110: {1,3,5}
114: {1,2,8}
120: {1,1,1,2,3}
130: {1,3,6}
132: {1,1,2,5}
138: {1,2,9}
MATHEMATICA
Select[Range[100], PrimeNu[#]>1&&!And@@EvenQ/@Take[Last/@FactorInteger[#], {2, -2}]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Dec 06 2021
STATUS
approved