A235812 a(n) is the start of the earliest run of n numbers such that the sum of their digits is equal to the sum of the digits of their prime factors.

2, 2, 2, 2, 1458855, 1790478, 429990136, 4475873320, 1979414080360

Offset

1,1

Comments

This sequence takes into account both primes and Smith numbers (A006753).

a(10) > 5*10^12.

Links

Table of n, a(n) for n=1..9.

C. Rivera, Puzzle 247. Consecutive Smith numbers

Example

The four numbers 2, 3, 4, 5 are either prime (2, 3, 5) or Smith (4) numbers. In any case, the sum of their digits is equal to the sum of their prime factors (counted with multiplicity), hence a(1) = a(2) = a(3) = a(4) = 2.

Crossrefs

Cf. A006753, A059754.

Sequence in context: A339017 A084957 A239944 * A343471 A035307 A292373

Adjacent sequences: A235809 A235810 A235811 * A235813 A235814 A235815

Keyword

nonn,base

Author

Giovanni Resta, Jan 16 2014

Status

approved