

A371808


Exponents k > 0 of powers of 2 such that the decimal expansion of 2^k contains more than one 666 substring (overlapping substrings are counted as distinct).


4



220, 222, 243, 529, 624, 648, 662, 702, 714, 838, 840, 842, 844, 846, 850, 857, 859, 867, 869, 871, 924, 925, 927, 929, 931, 975, 979, 981, 983, 1056, 1058, 1062, 1088, 1133, 1135, 1160, 1162, 1219, 1230, 1241, 1259, 1310, 1341, 1343, 1349, 1384, 1394, 1411, 1420
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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



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


CROSSREFS



KEYWORD

nonn,easy,base


AUTHOR



STATUS

approved



