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A337208
Indices m of repunits R_m that are Colombian (or self) numbers.
3
1, 4, 6, 17, 28, 39, 50, 61, 72, 83, 94, 109, 120, 131, 142, 153, 164, 175, 186, 197, 199, 210, 221, 232, 243, 254, 265, 276, 287, 298, 300, 311, 322, 333, 344, 355, 366, 377, 388, 399, 401, 412, 423, 434, 445, 456, 467, 478, 489, 500, 502, 513, 524, 535, 546, 557
OFFSET
1,2
LINKS
PROG
(PARI) upto(n)= {my(res = List()); for(i = 1, n, if(is(i), listput(res, i); print1(i", "))); res}
is(n) = {c = 10^n \ 9; is_A003052(c)}
is_A003052(n)={for(i=1, min(n\2, 9*#digits(n)), sumdigits(n-i)==i && return); n} \\ from M. F. Hasler, Mar 20 2011
CROSSREFS
Cf. A002275 (repunits), A003052 (Colombian (or self)), A004022 (repunit primes), A004023 (indices of repunit primes), complement of A337139.
Sequence in context: A024305 A342231 A320245 * A034492 A125691 A302878
KEYWORD
nonn,base
AUTHOR
David A. Corneth, Aug 19 2020
STATUS
approved