OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
EXAMPLE
For n = 16 = 2^4, sopfr(16) = 2*4 = 8 and 15 = 3 * 5, sopfr(15)= 3 + 5 = 8 and for k < 15, sopfr(k) != 8, hence a(16) = 15.
MATHEMATICA
f[n_] := Plus @@ Times @@@ FactorInteger[n]; f[1] = 0; m = 100; With[{s = Array[f, m]}, Table[FirstPosition[s, s[[n]]][[1]], {n, 1, m}]] (* Amiram Eldar, Aug 15 2022 *)
PROG
(PARI) sopfr(n) = (n=factor(n))[, 1]~*n[, 2]; \\ A001414
a(n) = my(s=sopfr(n), k=1); while (sopfr(k) != s, k++); k; \\ Michel Marcus, Aug 16 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Jean-Marc Rebert, Aug 15 2022
STATUS
approved