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A217410 Numbers of the form 3^r*7^s whose decimal representations are such that each digit 0-9 appears a prime number of times. 13
127194058437252046971768387, 13246352657250963177488450589, 1461157813024707015061910842923, 12415617112031938486785960616347, 147856680363717377959300292543841 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
See the formula section for more data, and the others in cross-reference for similar sequences and motivation.
LINKS
FORMULA
a(n) = 3^A217411(n) * 7^A217412(n).
EXAMPLE
A217411(1)=37 and A217412(1)=10, so this sequence's first term is (3^37)*(7^10). It is the smallest number with exactly 3 and 7 as its prime factors to have decimal representation with each digit 0-9 counted a prime number of times. The digits 0, 2, 3, 5, 6 and 9 occur two times each; 1, 4 and 8 occur three times each; and 7 occurs five times.
CROSSREFS
Sequence in context: A214266 A175274 A095446 * A338956 A338952 A323535
KEYWORD
nonn,base,less
AUTHOR
James G. Merickel, Oct 02 2012
STATUS
approved

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Last modified April 24 15:18 EDT 2024. Contains 371960 sequences. (Running on oeis4.)