A383675 Number of n-digit terms in A157711.

0, 0, 0, 0, 1, 0, 2, 2, 1, 4, 9, 5, 8, 3, 9, 9, 12, 6, 14, 4, 5, 9, 8, 10, 13, 10, 8, 19, 17, 15, 20, 16, 27, 16, 26, 14, 23, 18, 26, 22, 40, 23, 21, 18, 32, 24, 29, 15, 33, 21, 25, 33, 34, 25, 25, 22, 47, 30, 40, 25, 37, 29, 38, 33, 47, 30, 41, 37, 45, 41, 46, 33, 42, 36, 52, 39, 48, 28, 49, 37

Offset

1,7

Comments

The b-file terms are based on probable prime counts that have been verified correct (by counting proven primes) to index 200. Subsequent terms (as they get larger) seemingly face an increasing probability of counting a probable prime that is actually a composite but it is unknown if such probability is ever large enough to impact the intended proven prime count.

Links

Hans Havermann, Table of n, a(n) for n = 1..4000

Hans Havermann, Combined point/points-joined plot of 4000 terms

Example

There are two A157711 terms (1011001, 1100101) containing 7 digits, so a(7) = 2.

Crossrefs

Cf. A157711, A393531 (emirp pair counts).

Sequence in context: A137399 A158985 A295687 * A087854 A185041 A086873

Adjacent sequences: A383672 A383673 A383674 * A383676 A383677 A383678

Keyword

nonn,base

Author

Hans Havermann, May 29 2025

Status

approved