A045970 - OEIS

%I #14 Sep 19 2023 01:44:25

%S 7,11,13,121,17,143,19,1331,169,187,23,1573,29,209,221,14641,31,1859,

%T 37,2057,247,253,41,17303,289,319,2197,2299,43,2431,47,161051,299,341,

%U 323,20449,53,407,377,22627,59,2717,61,2783,2873,451,67,190333,361,3179,403

%N a(1)=7; if n = Product p_i^e_i, n > 1, then a(n) = Product p_{i+4}^e_i.

%D From a puzzle proposed by _Marc LeBrun_.

%t f[p_, e_] := NextPrime[p, 4]^e; a[1] = 7; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Sep 19 2023 *)

%Y Cf. A045965, A045966, A045967, A045968, A045969, A045971, A045972, A045973.

%K easy,nonn

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _David W. Wilson_