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.

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A319809 Numbers k that are equal to 2*k when expressed in base 9 and then interpreted in base 10.

Original entry on oeis.org

7794416, 7816758, 8131871, 8132006, 8152638, 8152650
Offset: 1

Views

Author

Anton Deynega, Sep 28 2018

Keywords

Examples

			8132006 expressed in base 9 is equal to 16264012; 16264012 = 2*8132006.

Crossrefs

Cf. A139285.

Programs

  • Mathematica
    Select[Range[10^6, 10^7], FromDigits@ IntegerDigits[#, 9] == 2 # &] (* Michael De Vlieger, Oct 11 2018 *)
  • PARI
    isok(n) = fromdigits(digits(n,9), 10) == 2*n; \\ Michel Marcus, Sep 28 2018

A378024 Smallest k >= 10 whose decimal representation read in base (n+10) is a multiple of k.

Original entry on oeis.org

1913268348854, 11788, 1557, 126357, 145, 1038, 1757, 116, 153, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10, 21, 11, 23, 12, 25, 13, 27, 14, 29, 10, 31, 16, 11, 17, 35, 12, 37, 19, 13, 10, 41, 14, 43, 11, 15, 23, 47, 12, 49, 10, 17, 13, 53, 18, 11, 14, 19, 29, 59, 10, 61
Offset: 1

Views

Author

Sergio Pimentel, Nov 14 2024

Keywords

Comments

This is a variation of A139285 that has terms beyond n=10.

Examples

			a(5)=145 because 145 read in base 15 is 1*15^2+4*15+5=290 = 2*145 and no other number below 145 has this property except for the trivial values < 10.

Crossrefs

Cf. A139285.

Programs

  • PARI
    a(n) = my(k=10); while(fromdigits(digits(k), n+10) % k, k++); k; \\ Michel Marcus, Nov 16 2024

Extensions

More terms from Michel Marcus, Nov 16 2024
Showing 1-2 of 2 results.

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