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A254715 Number of n-digit semiprimes with semiprime digits (4, 6, 9). 1
3, 4, 8, 18, 55, 137, 415, 941, 2854, 7743, 21959, 61545, 175817, 496688 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..14.

FORMULA

a(n) = number of n-digit terms in A107342.

EXAMPLE

a(1) = 3 because there are 3 one-digit semiprimes with semiprime digits: 4,6,9.

a(2) = 4 because there are 4 two-digit relevant semiprimes: 46,49,69,94.

a(3) = 8 because there are 8 three-digit relevant semiprimes: 446,466,469,649,669,694,699,949.

CROSSREFS

Cf. A107342.

Sequence in context: A183494 A107429 A061273 * A107328 A065034 A332707

Adjacent sequences:  A254712 A254713 A254714 * A254716 A254717 A254718

KEYWORD

nonn,base

AUTHOR

Zak Seidov, Feb 06 2015

STATUS

approved

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Last modified September 20 13:45 EDT 2020. Contains 337264 sequences. (Running on oeis4.)