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 1-3 of 3 results.

A292683 Numbers divisible by themselves with first digit removed (A217657), excluding multiples of 10.

Original entry on oeis.org

11, 12, 15, 21, 22, 24, 25, 31, 32, 33, 35, 36, 41, 42, 44, 45, 48, 51, 52, 55, 61, 62, 63, 64, 65, 66, 71, 72, 75, 77, 81, 82, 84, 85, 88, 91, 92, 93, 95, 96, 99, 101, 102, 104, 105, 125, 201, 202, 204, 205, 208, 225, 301, 302, 303, 304, 305, 306, 312, 315, 325, 375, 401, 402, 404, 405, 408, 416, 425, 501
Offset: 1

Views

Author

M. F. Hasler, Oct 17 2017

Keywords

Comments

Obviously, any term multiplied by 10 would again be a term, so we exclude trailing zeros.
This sequence cannot contain single-digit numbers (which would yield 0 with the initial digit removed), in contrast to A178158 (numbers divisible by every suffix of n) where the condition is vacuously satisfied for single-digit numbers.
416 is the first term in the present sequence which is not in A178158.
See A292684 and A292685 for the (number of) multiples of N = a(n) which have the same property and yield the same ratio N/A217657(N).

Examples

			12 is in the sequence because it is divisible by 2.
416 is in the sequence because it is divisible by 16, 416 = 4*4*25 + 16.
		

Crossrefs

Programs

  • Mathematica
    fQ[n_] := Mod[n, 10] > 0 && Mod[n, n - Quotient[n, 10^Floor@ Log10@ n] 10^Floor@ Log10@ n] == 0; Select[ Range[11, 501], fQ] (* Robert G. Wilson v, Oct 18 2017 *)
    Select[Range[10,550],Mod[#,10]!=0&&Mod[#,FromDigits[Rest[IntegerDigits[#]]]]==0&] (* Harvey P. Dale, Sep 15 2024 *)
  • PARI
    select( is(n)=n%10&&(m=n%10^logint(n,10))&&!(n%m), [0..500])

A210582 Numbers whose first digit is the remainder of their division by the last digit (in base 10).

Original entry on oeis.org

13, 19, 23, 26, 29, 39, 46, 49, 59, 69, 79, 89, 103, 109, 127, 133, 163, 193, 197, 199, 203, 206, 209, 214, 218, 233, 234, 236, 247, 254, 258, 263, 266, 274, 293, 294, 296, 298, 299, 309, 367, 399, 406, 409, 417, 428, 436, 466, 468, 487, 496, 499, 509, 537, 599, 609, 638, 657, 678, 699, 709, 799, 809, 899
Offset: 1

Views

Author

Eric Angelini and M. F. Hasler, Mar 22 2012

Keywords

Comments

This is a restricted or simplified version of the definition of modest numbers A054986.

Crossrefs

A subsequence of A067251, disjoint with A034709.

Programs

  • Haskell
    a210582 n = a210582_list !! (n-1)
    a210582_list = filter (\x -> mod x (a010879 x) == a000030 x) a067251_list
    -- Reinhard Zumkeller, Mar 26 2012
    
  • Magma
    [ n: n in [1..1002] | not IsZero(d[1]) and n mod d[1] eq d[#d] where d is Intseq(n) ];  // Bruno Berselli, Mar 26 2012
  • PARI
    is_nm( x )=x%10 && x%(x%10)==x\10^(#Str(x)-1)
    for(n=1,999,is_nm(n)&print1(n","))
    

Formula

a(n) mod A010879(a(n)) = A000030(a(n)). [Reinhard Zumkeller, Mar 26 2011]

Extensions

Edited by M. F. Hasler, Jan 14 2014

A261448 Numbers n >= 100 that are divisible by n mod 100.

Original entry on oeis.org

101, 102, 104, 105, 110, 120, 125, 150, 201, 202, 204, 205, 208, 210, 220, 225, 240, 250, 301, 302, 303, 304, 305, 306, 310, 312, 315, 320, 325, 330, 350, 360, 375, 401, 402, 404, 405, 408, 410, 416, 420, 425, 440, 450, 480, 501, 502, 504, 505, 510, 520, 525, 550
Offset: 1

Views

Author

Giovanni Teofilatto, Aug 19 2015

Keywords

Comments

This sequence can be seen as the union of 99 linear sequences of the form a_i*k+i, for i=1,...,99 and k>0, where a_i depends on i. For example, 100*k+1, 100*k+2, 300*k+3,..., 4700*k+94, 1900*k+95,..., 9900*k+99. Hence, in analogy with A034709, there exist two numbers p and q such that a(p*k+i) = q*k + a(i), where q <= lcm(1,2,...,99). - Giovanni Resta, Aug 20 2015

Crossrefs

Programs

  • Mathematica
    Select[Range[100, 1000], Quiet@ Divisible[#, Mod[#, 100]] &] (* Giovanni Resta, Aug 19 2015 *)
  • PARI
    isok(n) = (n>100) && (dd = n % 100) && !(n % dd); \\ Michel Marcus, Aug 19 2015

Extensions

More terms from Michel Marcus, Aug 19 2015
Showing 1-3 of 3 results.