OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 22 as 2 has only one prime factor, which is 2;
a(3) = 33 as 3 has only one prime factor, which is 3;
a(4) = 42 as 4 has only one distinct prime factor, which is 2;
a(5) = 55 as 5 has only one prime factor, which is 5;
a(6) = 623 as 6 has two distinct prime factors, which are 2 and 3; etc.
MAPLE
f:= proc(n) local P;
P:= sort(convert(numtheory:-factorset(n), list));
parse(cat(n, op(P)))
end proc:
f(1):= 10:
mao(f, [$1..100]); # Robert Israel, Mar 04 2024
MATHEMATICA
a[1] = 1; a[n_Integer?Positive] := Module[{p, t}, p = Sort[DeleteDuplicates[FactorInteger[n][[All, 1]]]]; t = FromDigits[Flatten[IntegerDigits /@ Prepend[p, n]]]; t]; Table[a[n], {n, 1, 48}] (* Robert P. P. McKone, Dec 04 2023 *)
CROSSREFS
KEYWORD
AUTHOR
Eric Angelini, Dec 04 2023
STATUS
approved