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A044072 Numbers k such that string 2,3 occurs in the base 4 representation of k but not of k-1. 3
11, 27, 43, 59, 75, 91, 107, 123, 139, 155, 171, 203, 219, 235, 251, 267, 283, 299, 315, 331, 347, 363, 379, 395, 411, 427, 459, 475, 491, 507, 523, 539, 555, 571, 587, 603, 619, 635, 651, 667, 683, 779, 795, 811, 827, 843, 859, 875, 891, 907, 923, 939, 971 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Members are of form 16k+11, but not all such numbers are in the sequence. The first missing number is 187.
LINKS
MATHEMATICA
Flatten[Position[Partition[Table[If[MemberQ[Partition[IntegerDigits[n, 4], 2, 1], {2, 3}], 1, 0], {n, 1000}], 2, 1], {0, 1}]] + 1 (* Vincenzo Librandi, Aug 19 2015 *)
PROG
(Python)
from sympy.ntheory.factor_ import digits
def has23(n): return "23" in "".join(map(str, digits(n, 4)[1:]))
def ok(n): return has23(n) and not has23(n-1)
print([k for k in range(972) if ok(k)]) # Michael S. Branicky, Nov 27 2021
CROSSREFS
Differs from A106839.
Cf. A044453.
Sequence in context: A152574 A035701 A106839 * A044453 A212776 A362528
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
a(48) and beyond from Michael S. Branicky, Nov 27 2021
STATUS
approved

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Last modified April 13 11:28 EDT 2024. Contains 371640 sequences. (Running on oeis4.)