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 A062664 Composite and every divisor (except 1) contains the digit 2. 18
 254, 422, 482, 502, 526, 529, 542, 562, 842, 1042, 1642, 2042, 2246, 2258, 2402, 2426, 2434, 2446, 2458, 2462, 2474, 2498, 2518, 2554, 2558, 2566, 2578, 2582, 2594, 2642, 2654, 2846, 2854, 2858, 2921, 3242, 3254, 3442, 4022, 4126, 4162, 4222, 4226 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If k is in the sequence, then all composite divisors of k are in the sequence. - Robert Israel, Jul 11 2019 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE 254 has divisors 1, 2, 127 and 254, all of which except 1 contain the digit 2. MAPLE filter:= proc(n) local D;   if isprime(n) then return false fi;   andmap(con2, numtheory:-divisors(n) minus {1}) end proc: con2:= proc(n) option remember; member(2, convert(n, base, 10)) end proc: select(filter, [\$4..10000]); # Robert Israel, Jul 11 2019 MATHEMATICA fQ[n_, dgt_] := Union[ MemberQ[#, dgt] & /@ IntegerDigits@ Rest@ Divisors@ n][[1]]; Select[ Range[2, 4230], !PrimeQ[#] && fQ[#, 2] &] (* Robert G. Wilson v, Jun 11 2014 *) PROG (MAGMA) [m:m in [2..4300] | not IsPrime(m) and #[d:d in Divisors(m)|2 in Intseq(d)] eq #Divisors(m)-1]; // Marius A. Burtea, Jul 11 2019 CROSSREFS Cf. A062649, A062668, A062670, A062672, A062674, A062676, A062678, A062680, A243819. Sequence in context: A263380 A144855 A110827 * A258696 A158249 A255178 Adjacent sequences:  A062661 A062662 A062663 * A062665 A062666 A062667 KEYWORD base,easy,nonn AUTHOR Erich Friedman, Jul 04 2001 EXTENSIONS Offset changed by Robert Israel, Jul 11 2019 STATUS approved

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Last modified January 23 12:31 EST 2021. Contains 340385 sequences. (Running on oeis4.)