OFFSET
1,3
LINKS
FORMULA
EXAMPLE
Here primepi (A000720) gives the index of its prime argument:
n = 14 = 2 * 7, thus a(14) = lcm(primepi(2), primepi(7)) = lcm(1,4) = 4.
n = 21 = 3 * 7, thus a(21) = lcm(primepi(3), primepi(7)) = lcm(2,4) = 4.
MATHEMATICA
Table[Apply[LCM, PrimePi[FactorInteger[n][[All, 1]] ]] + Boole[n == 1], {n, 105}] (* Michael De Vlieger, Aug 14 2017 *)
PROG
(Scheme) (define (A290103 n) (if (= 1 n) n (lcm (A055396 n) (A290103 (A028234 n))))) ;; Antti Karttunen, Aug 13 2017
(PARI) a(n)=if(n>1, lcm(apply(primepi, factor(n)[, 1])), 1) \\ Charles R Greathouse IV, Nov 11 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 13 2017
STATUS
approved