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.

A119170 Triangular numbers composed of digits {2,5,9}.

Original entry on oeis.org

55, 595, 5995, 255255, 292995, 299925, 25952229225, 99292929555225, 55955525255559595, 555959229929999252295, 925952955522559552259925, 5299552922255552929595999295, 5995959559225555222929295255522595295, 9925559955529295222599225259529552225
Offset: 1

Views

Author

Giovanni Resta, May 10 2006

Keywords

Comments

a(15) > 10^40. - Tyler Busby, Mar 24 2023

Links

Crossrefs

Cf. A000217, A053929, A119171. See A119033 for a table of cross-references.

Programs

  • Mathematica
    Flatten[Table[Select[FromDigits /@ Tuples[{2, 5, 9}, n], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &], {n, 11}]] (* Amiram Eldar, Nov 30 2018 *)

Formula

a(n) = A000217(A119171(n)).
a(n) == 5 (mod 10) for all n. - Chai Wah Wu, Nov 30 2018

Extensions

a(13)-a(14) from Tyler Busby, Mar 24 2023

A053928 Numbers k such that k^2 contains only digits {2,5,9}.

Original entry on oeis.org

3, 5, 15, 23, 77, 173, 235, 315, 1515, 2435, 7227, 23515, 54335, 97773, 243515, 2435077, 3090673, 72497765, 74533585, 9639636523, 979793819766485, 77170285247817565, 9794365502654705173, 1598601020441309256565, 30484348812550551609088485, 76975943837016723668817565
Offset: 1

Views

Author

Patrick De Geest, Mar 15 2000

Keywords

Links

Crossrefs

Cf. A053929.

Extensions

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 14 2005
a(21)-a(24) from Mishima's page added by Max Alekseyev, Aug 18 2013
More terms from Zhao Hui Du, Mar 01 2024
Showing 1-2 of 2 results.

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

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