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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A078243 Smallest multiple of n using only digits 0 and 4.

Original entry on oeis.org

4, 4, 444, 4, 40, 444, 4004, 40, 444444444, 40, 44, 444, 4004, 4004, 4440, 400, 44404, 444444444, 44004, 40, 40404, 44, 440404, 4440, 400, 4004, 4404444444, 4004, 4404404, 4440, 444044, 4000, 444444, 44404, 40040, 444444444, 444, 44004, 40404
Offset: 1

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Author

Amarnath Murthy, Nov 23 2002

Keywords

Comments

a(n) = min{A169967(k): k > 1 and A169967(k) mod n = 0}. [Reinhard Zumkeller, Jan 10 2012]

Crossrefs

Programs

  • Haskell
    a078243 n = head [x | x <- tail a169967_list, mod x n == 0]
    -- Reinhard Zumkeller, Jan 10 2012

Extensions

More terms from Ray Chandler, Jul 12 2004

A268620 Numbers whose digital sum is a multiple of 4.

Original entry on oeis.org

0, 4, 8, 13, 17, 22, 26, 31, 35, 39, 40, 44, 48, 53, 57, 62, 66, 71, 75, 79, 80, 84, 88, 93, 97, 103, 107, 112, 116, 121, 125, 129, 130, 134, 138, 143, 147, 152, 156, 161, 165, 169, 170, 174, 178, 183, 187, 192, 196, 202, 206, 211, 215, 219, 220, 224, 228, 233, 237, 242, 246
Offset: 1

Views

Author

Bruno Berselli, Feb 09 2016

Keywords

Comments

a(1498) = 5999 is the smallest term that is congruent to 5 modulo 9.

Crossrefs

Cf. A007953, A061383 (supersequence).
Cf. numbers whose digital sum is a multiple of k: A054683 (k=2), A008585 (k=3), this sequence (k=4), A227793 (k=5).

Programs

  • Magma
    [n: n in [0..250] | IsIntegral(&+Intseq(n)/4)];
  • Maple
    select(t -> convert(convert(t,base,10),`+`) mod 4 = 0, [$1..1000]); # Robert Israel, Feb 09 2016
  • Mathematica
    Select[Range[0, 250], IntegerQ[Total[IntegerDigits[#]]/4] &]

A284972 Numbers with digits 4 and 8 only.

Original entry on oeis.org

4, 8, 44, 48, 84, 88, 444, 448, 484, 488, 844, 848, 884, 888, 4444, 4448, 4484, 4488, 4844, 4848, 4884, 4888, 8444, 8448, 8484, 8488, 8844, 8848, 8884, 8888, 44444, 44448, 44484, 44488, 44844, 44848, 44884, 44888, 48444, 48448, 48484, 48488, 48844, 48848
Offset: 1

Views

Author

Jaroslav Krizek, Apr 07 2017

Keywords

Comments

All terms are even.

Crossrefs

Numbers with digits 4 and k only for k = 0 - 3 and 5 - 9: A169967 (k = 0), A032822 (k = 1), A284920 (k = 2), A032834 (k = 3), A256290 (k = 5), A284634 (k = 6), A284971 (k = 7), this sequence (k = 8), A284973 (k = 9).

Programs

  • Magma
    [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {4, 8}]
    
  • Mathematica
    Flatten@ Table[FromDigits /@ Tuples[{4, 8}, n], {n, 5}] (* Giovanni Resta, Apr 07 2017 *)
  • PARI
    a(n) = my (b = binary(1+n)); b[1] = 0; return (4*(10^(#b-1)-1)/(10-1) + (8-4)*fromdigits(b)) \\ Rémy Sigrist, Apr 08 2017
    
  • PARI
    a(n)={my(v=binary(n+1));v[1]=0;v+=vector(#v,i,i>1);4*fromdigits(v)} \\ R. J. Cano, Apr 08 2017
    
  • PARI
    a(n,{p=[4,8]})={my(v=binary(n+1));fromdigits(vector(#v-1,i,p[2]*v[i+1]+p[1]*!v[i+1]))} \\ R. J. Cano, Apr 09 2017

Formula

a(n) = 2 * A284920(n) = 4 * A032822(n).
Previous Showing 11-13 of 13 results.