cp's OEIS Frontend

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.

Showing 1-2 of 2 results.

A100414 Numbers n such that n is R(n)-th composite number where R(n) is the digit reversal of n (A002808(A004086(n))=n).

Original entry on oeis.org

21, 48034, 69926, 180461, 214591, 409473, 563715, 41630193, 253385633342, 661494322636
Offset: 1

Views

Author

Farideh Firoozbakht, Dec 10 2004

Keywords

Comments

There is no further term < 3*10^9.
a(11) > 3*10^12. [Donovan Johnson, Jun 14 2009]

Examples

			41630193 is in the sequence because 41630193 is the 39103614th composite number.

Crossrefs

Cf. A002808, A004086, A100412, A100413, A100415.

Programs

  • Mathematica
    Do[s=FromDigits[Reverse[IntegerDigits[n]]];If[s

Extensions

a(9)-a(10) from Donovan Johnson, Jun 14 2009

A114926 Numbers n such that pi(n)=reversal(n)-n.

Original entry on oeis.org

1, 23, 526, 536, 1802, 4735, 17191, 38524, 235652, 36235483, 1086331411, 5316125655, 7202194357, 49294058315, 327040088933
Offset: 1

Views

Author

Farideh Firoozbakht, Feb 03 2006

Keywords

Comments

a(16) > 10^13. - Giovanni Resta, Aug 08 2019

Examples

			36235483 is in the sequence because pi(36235483)=2217780= 38453263-36235483=reversal(36235483)-36235483.

Crossrefs

Cf. A072393, A100415.

Programs

  • Mathematica
    Do[If[PrimePi[n]==FromDigits[Reverse[IntegerDigits[n]]] -n,Print[n]],{n,30000000}]

Extensions

a(11)-a(15) from Giovanni Resta, Aug 08 2019
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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