

A217410


Numbers of the form 3^r*7^s whose decimal representations are such that each digit 09 appears a prime number of times.


13




OFFSET

1,1


COMMENTS

See the formula section for more data, and the others in crossreference for similar sequences and motivation.


LINKS



FORMULA



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 09 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

Cf. A216854, A217411, A217412, A217404, A217407, A217410, A217416, A217419, A217422, A217425, A217428, A217431.


KEYWORD

nonn,base,less


AUTHOR



STATUS

approved



