A393264 The smallest number k > 1 such that the total number of its prime factors, with multiplicity, equals that of the digit reversals of k when it is written in all bases 2 to n.

3, 5, 5, 7, 7, 67, 67, 67, 9077, 28129, 28129, 28129, 504199, 1861487, 1861487, 1861487, 344430565, 6277783214

Offset

2,1

Links

Table of n, a(n) for n=2..19.

Example

a(7) = 67 as the total number of prime factors, with multiplicity, of 67 is 1, while with digital reversals of 67 in base 2, 3, 4, 5, 6, 7 are 97, 41, 193, 67, 67, 211 respectively, all of which have one prime factor. No smaller number satisfies this criterion.

Prog

(PARI) isok(k, n) = my(v=vector(n-1, b, bigomega(fromdigits(Vecrev(digits(k, b+1)), b+1)))); (#Set(v) == 1) && (v[1] == bigomega(k));
a(n) = my(k=2); while(!isok(k, n), k++); k; \\ Michel Marcus, Feb 16 2026

Crossrefs

Cf. A001222, A393263, A393176.

Sequence in context: A393263 A168322 A396962 * A138475 A195990 A023840

Adjacent sequences: A393261 A393262 A393263 * A393265 A393266 A393267

Keyword

nonn,base,more

Author

Scott R. Shannon, Feb 07 2026

Status

approved