

A108636


Semiprimes with even digits.


1



4, 6, 22, 26, 46, 62, 82, 86, 202, 206, 226, 262, 422, 446, 466, 482, 622, 626, 662, 802, 842, 862, 866, 886, 2026, 2042, 2062, 2066, 2206, 2246, 2402, 2426, 2446, 2462, 2602, 2606, 2642, 2846, 2866, 4006, 4022, 4222, 4226, 4262, 4282, 4286, 4406, 4426, 4442
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OFFSET

1,1


COMMENTS

Semiprimes with even digits are less numerous than those with odd digits, cf. A091296.
"Semiprimes with even digits are less numerous than those with odd digits" because (base 10): no integer after 10 can end in a 0 without being divisible by 2, 5 and at least one other prime; for a semiprime to end in 2, 4, 6, or 8 it must be divisible by 2 and a prime with almost as many digits as the semiprime (and primes get rarer as they get longer); no semiprime with all even digits after 22 can be a repdigit; and similar constraints.  Jonathan Vos Post, Nov 07 2005


LINKS

Table of n, a(n) for n=1..49.


MATHEMATICA

Select[Range[6000], Plus@@Last/@FactorInteger[ # ]==2&&Union[EvenQ/@IntegerDigits[ # ]]=={True}&]


CROSSREFS

Cf. A091296.
Sequence in context: A002270 A088228 A272309 * A101143 A083157 A192154
Adjacent sequences: A108633 A108634 A108635 * A108637 A108638 A108639


KEYWORD

nonn,base


AUTHOR

Zak Seidov, Jun 14 2005


STATUS

approved



