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Search: id:A108636
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| A108636 |
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Semiprimes with even digits. |
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+0
2
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| 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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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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 (jvospost3(AT)gmail.com), Nov 07 2005
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MATHEMATICA
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Select[Range[6000], Plus@@Last/@FactorInteger[ # ]==2&&Union[EvenQ/@IntegerDigits[ # ]]=={True}&]
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CROSSREFS
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Cf. A091296.
Sequence in context: A151520 A002270 A088228 this_sequence A101143 A083157 A151519
Adjacent sequences: A108633 A108634 A108635 this_sequence A108637 A108638 A108639
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KEYWORD
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nonn,base
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Jun 14 2005
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