A329025 If n = Product (p_j^k_j) then a(n) = concatenation (pi(p_j)), where pi = A000720.

0, 1, 2, 1, 3, 12, 4, 1, 2, 13, 5, 12, 6, 14, 23, 1, 7, 12, 8, 13, 24, 15, 9, 12, 3, 16, 2, 14, 10, 123, 11, 1, 25, 17, 34, 12, 12, 18, 26, 13, 13, 124, 14, 15, 23, 19, 15, 12, 4, 13, 27, 16, 16, 12, 35, 14, 28, 110, 17, 123, 18, 111, 24, 1, 36, 125, 19, 17, 29, 134

Offset: 1

Author

Ilya Gutkovskiy, Nov 02 2019

Keywords

• nonn
• base

Comments

Concatenate of indices of distinct prime factors of n, in increasing order.

Examples

			a(60) = a(2^2 * 3 * 5) = a(prime(1)^2 * prime(2) * prime(3)) = 123.
		

Links

• Ilya Gutkovskiy, Scatter plot of a(n) up to n=100000
• Index entries for sequences computed from indices in prime factorization

Crossrefs

Cf. A000720, A037916, A080695, A084317, A127668, A304038, A329026.

Programs

Mathematica

a[n_] := FromDigits[Flatten@IntegerDigits@(PrimePi[#[[1]]] & /@ FactorInteger[n])]; Table[a[n], {n, 1, 70}]

Formula

a(prime(n)^k) = n for k > 0.