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A329025
If n = Product (p_j^k_j) then a(n) = concatenation (pi(p_j)), where pi = A000720.
2
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
1,3
COMMENTS
Concatenate of indices of distinct prime factors of n, in increasing order.
FORMULA
a(prime(n)^k) = n for k > 0.
EXAMPLE
a(60) = a(2^2 * 3 * 5) = a(prime(1)^2 * prime(2) * prime(3)) = 123.
MATHEMATICA
a[n_] := FromDigits[Flatten@IntegerDigits@(PrimePi[#[[1]]] & /@ FactorInteger[n])]; Table[a[n], {n, 1, 70}]
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Nov 02 2019
STATUS
approved