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A284632
Numbers n with digits 2 and 6 only.
9
2, 6, 22, 26, 62, 66, 222, 226, 262, 266, 622, 626, 662, 666, 2222, 2226, 2262, 2266, 2622, 2626, 2662, 2666, 6222, 6226, 6262, 6266, 6622, 6626, 6662, 6666, 22222, 22226, 22262, 22266, 22622, 22626, 22662, 22666, 26222, 26226, 26262, 26266, 26622, 26626
OFFSET
1,1
COMMENTS
All terms after 2 are composite.
FORMULA
a(n) = 2 * A032917(n).
MATHEMATICA
Table[Map[FromDigits, Tuples[{2, 6}, {k}]], {k, 5}] // Flatten (* Michael De Vlieger, Mar 30 2017 *)
PROG
(Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {2, 6}]
CROSSREFS
Cf. A032917.
Numbers n with digits 6 and k only for k = 0..5 and 7..9: A204093 (k = 0), A284293 (k = 1), this sequence (k = 2), A284633 (k = 3), A284634 (k = 4), A256291 (k = 5), A256292 (k = 7), A284635 (k = 8), A284636 (k = 9).
Sequence in context: A216719 A085286 A062085 * A350553 A325020 A335131
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Mar 30 2017
STATUS
approved