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 A050607 Numbers n such that base 5 expansion matches (0|1|2)*((0|1)(3|4))?(0|1|2)* 3
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 16, 17, 20, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 40, 41, 42, 45, 46, 47, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 75, 76, 77, 80, 81, 82, 85, 86, 87, 100, 101, 102, 105, 106, 107, 110, 111, 112, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 140, 141, 142, 145 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 25 does not divide C(2s-1,s) = A001700[ s ] (nor C(2s,s) = A000984[ s ], central column of Pascal's Triangle) if and only if s is one of the terms in this sequence. LINKS PROG (Perl) sub conv_x_base_n { my(\$x, \$b) = @_; my (\$r, \$z) = (0, ''); do { \$r = \$x % \$b; \$x = (\$x - \$r)/\$b; \$z = "\$r" . \$z; } while(0 != \$x); return(\$z); } for(\$i=1; \$i <= 201; \$i++) { if(("0" . conv_x_base_n(\$i, 5)) =~ /^(0|1|2)*((0|1)(3|4))?(0|1|2)*\$/) { print \$i, ", "; } } CROSSREFS Cf. A037453, A046097, A050608. Sequence in context: A003964 A023781 A135578 * A238368 A342164 A263808 Adjacent sequences:  A050604 A050605 A050606 * A050608 A050609 A050610 KEYWORD nonn,easy,base AUTHOR Antti Karttunen, Oct 24 1999 STATUS approved

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Last modified June 14 09:06 EDT 2021. Contains 345018 sequences. (Running on oeis4.)