A380375 - OEIS

%I #11 Jan 25 2025 12:37:33

%S 1,2,2,3,2,4,2,4,3,1,11,12,12,13,12,14,12,14,13,2,21,22,22,23,22,24,

%T 22,24,23,2,21,22,22,23,22,24,22,24,23,3,31,32,32,33,32,34,32,34,33,2,

%U 21,22,22,23,22,24,22,24,23,4,41,42,42,43,42,44,42,44,43,2,21,22,22,23,22,24,22,24,23

%N Delete all 0's from n, then replace each remaining digit k of n by A000005(k).

%C Numbers including only the digits 1,2,3,4.

%F a(10^n) = 1.

%e n = 10: delete 0, replace digit 1 by A000005(1), thus a(10) = 1.

%e n = 24: replace digit 2 by A000005(2), replace digit 3 by A000005(3), thus a(22) = 22.

%t a[n_] := FromDigits[DivisorSigma[0, DeleteCases[IntegerDigits[n], 0]]]; Array[a, 100] (* _Amiram Eldar_, Jan 23 2025 *)

%Y Cf. A000005, A004719.

%K nonn,base

%O 1,2

%A _Ctibor O. Zizka_, Jan 23 2025