A220480 - OEIS

%I #19 Jan 14 2021 20:36:39

%S 5,15,36,52,48,34,18,11,5

%N The number of n-digit numbers where last k digits are divisible by the k-th prime for k = 1..n.

%C There are total 224 numbers and 224246090, 632258960, 824791960, 851750490, and 904719030 are the only 9-digit numbers to satisfy the requirement.

%e There are five one-digit numbers divisible by the first prime so a(1)=5.

%e For two-digit numbers, the second digit must make it divisible by 3 which gives 15 numbers: 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96 to satisfy the requirement. So a(2)=15.

%Y Cf. A079212.

%K nonn,base,fini,full

%O 1,1

%A _Shyam Sunder Gupta_, Aug 07 2013