OFFSET
1,1
COMMENTS
Also numbers n such that both n and n+1 are in the same row of A215366.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..1000
EXAMPLE
44 is in the sequence because 44 = 2^2 * 11 = prime(1)^2 * prime(5) => f(44) = 1*2+5 = 7 and 44+1 = 45 = 3^2*5 = prime(2)^2 * prime(3) => f(45) = 2*2+3 = 7.
MAPLE
f:= n-> add(numtheory[pi](i[1])*i[2], i=ifactors(n)[2]):
a:= proc(n) option remember; local k;
for k from 1+ `if`(n=1, 0, a(n-1))
while f(k)<>f(k+1) do od; k
end:
seq(a(n), n=1..70);
MATHEMATICA
f[n_] := Sum[PrimePi[i[[1]]]*i[[2]], {i, FactorInteger[n]}];
a[n_] := a[n] = (For[k = 1 + If[n==1, 0, a[n-1]], f[k] != f[k+1], k++]; k);
Array[a, 70] (* Jean-François Alcover, Mar 22 2017, translated from Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 09 2012
STATUS
approved