A393531 Number of n-digit emirp pairs in A393530.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 1, 1, 2, 1, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 2, 1, 0, 0, 0, 0, 0, 0, 7, 1, 0, 1, 1, 2, 2, 0, 3, 0, 1, 1, 0, 0, 0, 0, 2, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 2, 1, 0, 0, 1, 0, 0, 0, 1, 2, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1

Offset

1,12

Comments

The first 1000 terms comprise 533 zeros, 324 ones, 113 twos, 25 threes, 3 fours, 1 five, and 1 seven, thus representing 649 emirp pairs.

The second 1000 terms comprise 518 zeros, 322 ones, 120 twos, 36 threes, 3 fours, and 1 five, representing an additional 687 emirp pairs. - Hans Havermann, May 15 2026

Links

Hans Havermann, Table of n, a(n) for n = 1..2000

Example

a(41) = 7 because there are seven 41-digit emirp pairs in A393530: (10^40+10^10+10^3+1, 10^40+10^37+10^30+1), (10^40+10^14+10^12+1, 10^40+10^28+10^26+1), (10^40+10^19+10^14+1, 10^40+10^26+10^21+1), (10^40+10^23+10^8+1, 10^40+10^32+10^17+1), (10^40+10^24+10^1+1, 10^40+10^39+10^16+1), (10^40+10^26+10^5+1, 10^40+10^35+10^14+1), (10^40+10^30+10^8+1, 10^40+10^32+10^10+1).

Crossrefs

Cf. A006567, A157711, A383675, A393530.

Sequence in context: A337683 A362451 A092673 * A243842 A367405 A112400

Adjacent sequences: A393528 A393529 A393530 * A393532 A393533 A393534

Keyword

nonn,base

Author

Hans Havermann, Feb 19 2026

Status

approved