OFFSET
1,6
COMMENTS
a(n) + 2 appears to differ from A000005 at n=1 and when n is a term of A320632. Verified up to n=3000.
If A320632 contains the numbers such that A001222(n) - A051903(n) > 1, then this sequence contains precisely the numbers p^k and p^k*q for distinct primes p and q. The comment follows, since d(p^k) = k+1 = (k-1)*1 + 2 and d(p^k*q) = 2k+2 = ((k+1)-1)*2 + 2. - Charlie Neder, May 14 2019
Positions of first appearances are A328965. - Gus Wiseman, Nov 05 2019
Regarding Neder's comment above, see also my comments in A322437. - Antti Karttunen, Feb 17 2021
LINKS
FORMULA
MATHEMATICA
a[n_] := (PrimeOmega[n] - 1)*PrimeNu[n];
aa = Table[a[n], {n, 1, 104}];
PROG
(PARI) a(n) = (bigomega(n) - 1)*omega(n); \\ Michel Marcus, May 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Mats Granvik, Apr 07 2019
STATUS
approved