OFFSET
1,1
COMMENTS
A positive power of 2 containing 666 in its decimal expansion is called an apocalyptic number.
See A371806 for a variant counting only nonoverlapping substrings.
LINKS
Paolo Xausa, Table of n, a(n) for n = 1..10000
Brady Haran and Tony Padilla, Apocalyptic Numbers, YouTube Numberphile video, 2024.
Eric Weisstein's World of Mathematics, Apocalyptic Number.
EXAMPLE
243 is a term because 2^243 contains two (overlapping) 666 substrings in its decimal expansion:
.
***
14134776518227074636666380005943348126619871175004951664972849610340958208.
***
MATHEMATICA
Select[Range[2000], StringCount[IntegerString[2^#], "666", Overlaps->True] > 1 &]
PROG
(Python)
def ok(n): return (s:=str(1<<n)).count("666") > 1 or "6666" in s
print([k for k in range(2000) if ok(k)]) # Michael S. Branicky, Apr 07 2024
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Paolo Xausa, Apr 06 2024
STATUS
approved