A217591 Absolute differences between emirps (A006567) and their reversals.

18, 54, 18, 36, 54, 36, 18, 18, 594, 198, 792, 594, 594, 792, 792, 198, 396, 396, 594, 594, 594, 198, 396, 198, 396, 594, 594, 198, 198, 198, 792, 594, 198, 792, 594, 792, 7992, 180, 270, 2268, 540, 8532, 810, 6804, 1908, 7902, 360, 2358, 630, 2718, 180, 1908, 5904, 1998, 7992, 90, 6084, 8172, 8262, 8442

Offset

1,1

Comments

This is unsorted, and in order of appearance of emirps.

All values are multiples of 18 (A008600). - Charles R Greathouse IV, Oct 15 2012

Links

Table of n, a(n) for n=1..60.

Formula

a(n) = | A006567(n) - R(A006567(n)) | = | A006567(n) - A004086(A006567(n)) |.

Example

a(1) = absolute value of first emirp versus its reversal = |13 - 31| = |-18| = 18.
a(2) = |17 - 71| = |-54| = 54.
a(3) = |31 - 13| = |18| = 18.
a(4) = |37 - 73| = |-36| = 36.

Maple

R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
q:= n-> isprime(n) and (p-> p<>n and isprime(p))(R(n)):
map(x-> abs(x-R(x)), select(q, [$2..1280]))[];  # Alois P. Heinz, Jul 12 2024

Crossrefs

Cf. A004086, A006567, A008600, A217286, A217386, A217387.

Sequence in context: A367345 A052495 A052902 * A059137 A346756 A096011

Adjacent sequences: A217588 A217589 A217590 * A217592 A217593 A217594

Keyword

nonn,base,easy

Author

Jonathan Vos Post, Oct 07 2012

Extensions

Corrected and more terms from Georg Fischer, Jul 12 2024

Status

approved