OFFSET
1,1
COMMENTS
A positive power of 2 containing 666 in its decimal expansion is called an apocalyptic number.
See A371808 for a variant where overlapping substrings are counted as distinct.
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
220 is a term because 2^220 contains more than one nonoverlapping 666 substring in its decimal expansion:
2^220 = 168499(666)66969149871(666)88442938726917102321526408785780068975640576.
MATHEMATICA
Select[Range[2000], StringCount[IntegerString[2^#], "666"] > 1 &]
PROG
(Python)
def ok(n): return str(1<<n).count("666") > 1
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