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A344145
Positive numbers m such that A020330^k(m) belongs to A344022 for any k >= 0 (where f^k denotes the k-th iterate of f).
2
2, 9, 10, 12, 35, 37, 38, 41, 42, 44, 49, 50, 52, 56, 139, 141, 142, 147, 149, 150, 153, 154, 156, 163, 165, 166, 169, 170, 172, 177, 178, 180, 184, 197, 198, 201, 202, 204, 209, 210, 212, 216, 226, 228, 232, 555, 557, 558, 563, 565, 566, 569, 570, 587, 589
OFFSET
1,1
COMMENTS
The binary expansion of a term, say (b_1, ..., b_m), encodes an m-periodic nonintersecting infinite walk made of unit steps, with a +90-degree turn (resp. a -90-degree turn) at positions X=k' such that b_k = 1 (resp. b_k = 0) with k = k' mod m.
All positive terms of A002450 belong to this sequence.
EXAMPLE
See illustration in Links section.
PROG
(PARI) is(n) = { my (b=if (n, binary(n), [0]), d=1, s=[d], z=2*d); b=concat([b, b, b, b]); for (k=1, #b, if (b[k], d*=I, d/=I); if (setsearch(s, z+=d), return (0), s=setunion(s, [z]); z+=d)); return (1) }
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, May 10 2021
STATUS
approved