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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

Original entry on oeis.org

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

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Author

Jonathan Vos Post, Oct 07 2012

Keywords

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

Examples

			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.

Crossrefs

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

Programs

  • 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

Formula

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

Extensions

Corrected and more terms from Georg Fischer, Jul 12 2024

A217610 Emirps (A006567) whose difference with the reversal is a perfect 4th power (A000583).

Original entry on oeis.org

1100090011, 1100900011, 1103093011, 1103903011, 1154094511, 1154904511, 1213093121, 1213903121, 1304094031, 1304904031, 1364094631, 1364904631, 1367097631, 1367907631, 1421091241, 1421901241, 1450090541, 1450900541, 1466096641, 1466906641, 1495095941, 1495905941, 1498098941, 1498908941
Offset: 1

Views

Author

Jonathan Vos Post, Oct 06 2012

Keywords

Comments

This is to A217387 as perfect 4th powers (A000583) are to perfect cubes (A000578), and as A217386 is to perfect squares (A000290). Subset of A217386, since every perfect 4th power is a perfect square (though not vice versa). In these terms all the difference are equal to 30^4.
Values a(1) through a(24) supplied by Giovanni Resta.

Crossrefs

Cf. A004086, A006567, A217286, A217386, A217387, 217591.
Showing 1-2 of 2 results.

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