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A165956 a(0) = 1. For n >= 1, a(n) = the number of earlier terms that, when written in binary, are substrings in binary n. 1
1, 1, 2, 2, 4, 4, 4, 2, 8, 8, 5, 6, 9, 7, 7, 4, 11, 11, 10, 10, 12, 8, 9, 10, 14, 13, 11, 11, 14, 12, 10, 4, 13, 13, 13, 13, 12, 13, 13, 14, 18, 17, 10, 15, 19, 18, 16, 13, 18, 18, 20, 17, 26, 21, 19, 21, 22, 21, 26, 24, 20, 21, 12, 5, 14, 14, 14, 14, 15, 17, 17, 19, 19, 16, 23, 22, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
If we instead had an offset of 1 and a(1)=1, then we would have sequence A122954.
LINKS
EXAMPLE
13 in binary is 1101. The earlier terms that, when written in binary, are substrings in 1101 are: a(0)=1, a(1)=1, a(2) = 2 = 10 in binary, a(3) = 2 = 10 in binary, a(7) = 2 = 10 in binary, a(10) = 5 = 101 in binary, and a(11) = 6 = 110 in binary. There are 7 such terms, so a(13) = 7.
PROG
(Python)
from collections import Counter
def A165956_list(nmax):
A, C = [1], Counter()
for n in range(1, nmax+1):
b = bin(n)[2:]
C.update({bin(A[-1])[2:]})
A.append(sum(C[i] for i in C if b.find(i) != -1))
return A # John Tyler Rascoe, Mar 11 2023
CROSSREFS
Cf. A122954.
Sequence in context: A042946 A037202 A227091 * A263991 A065285 A302437
KEYWORD
base,nonn
AUTHOR
Leroy Quet, Oct 01 2009
EXTENSIONS
More terms from Sean A. Irvine, Nov 09 2009
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)