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 A045067 Numbers whose base-4 representation contains exactly one 0 and one 3. 2
 12, 19, 28, 35, 44, 49, 50, 52, 56, 71, 75, 77, 78, 83, 92, 99, 108, 113, 114, 116, 120, 135, 139, 141, 142, 147, 156, 163, 172, 177, 178, 180, 184, 197, 198, 201, 202, 209, 210, 212, 216, 225, 226, 228, 232, 279, 283, 285, 286, 295, 299, 301, 302, 309, 310 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE F:= proc(d) local m; sort([seq(g(convert(m, base, 2)), m=2^d .. 2^(d+1)-1)]) end proc: g:= proc(L1) local i, k0, k3, nL, Res, L, Lp, Lpp; L:= map(`+`, L1[1..-2], 1); nL:= nops(L); Res:= NULL; for k3 from 0 to nL do Lp:= [op(L[1..k3]), 3, op(L[k3+1..nL])]; for k0 from 0 to nL do Lpp:= [op(Lp[1..k0]), 0, op(Lp[k0+1..nL+1])]; Res:= Res, add(Lpp[i]*4^(i-1), i=1..nL+2); od od; end proc: seq(op(F(d)), d=0..4); # Robert Israel, Jul 10 2019 PROG (Python) from sympy.ntheory import count_digits def ok(n): c = count_digits(n, 4); return c[0] == c[3] == 1 print([k for k in range(311) if ok(k)]) # Michael S. Branicky, Dec 19 2021 CROSSREFS Cf. A007090. Subsequence of A039279. Sequence in context: A349986 A043102 A039279 * A043882 A205718 A117539 Adjacent sequences: A045064 A045065 A045066 * A045068 A045069 A045070 KEYWORD nonn,base AUTHOR Clark Kimberling STATUS approved

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Last modified June 15 03:12 EDT 2024. Contains 373402 sequences. (Running on oeis4.)