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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
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
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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