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 1-4 of 4 results.

A190311 Number of nonzero digits when writing n in base where place values are positive cubes, cf. A000433.

Original entry on oeis.org

0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3
Offset: 0

Views

Author

Reinhard Zumkeller, May 08 2011

Keywords

Comments

For n > 0: a(A000578(n)) = 1; for n > 1: a(A001093(n)) = 2;
a(n) <= A048766(n).

Crossrefs

Programs

  • Haskell
    a190311 n = g n $ reverse $ takeWhile (<= n) $ tail a000578_list where
      g _ []                 = 0
      g m (x:xs) | x > m     = g m xs
                 | otherwise = signum m' + g r xs where (m',r) = divMod m x

A055401 Number of positive cubes needed to sum to n using the greedy algorithm.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 8, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 5, 1, 2, 3, 4, 5, 6, 7, 8, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 5, 6, 7, 8, 9, 10, 4, 5, 6, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 1, 2, 3, 4, 5, 6, 7, 8, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 5, 6, 7, 8, 9, 10, 4, 5, 6, 2, 3, 4, 5, 6, 7, 8, 9, 3, 4, 5, 6, 7
Offset: 0

Views

Author

Henry Bottomley, May 16 2000

Keywords

Comments

Define f(n) = n - k^3 where (k+1)^3 > n >= k^3; a(n) = number of steps such that f(f(...f(n)))= 0.
Also sum of digits when writing n in base where place values are positive cubes, cf. A000433. [Reinhard Zumkeller, May 08 2011]

Examples

			a(32)=6 because 32=27+1+1+1+1+1 (not 32=8+8+8+8).
a(33)=7 because 33=27+1+1+1+1+1+1 (not 33=8+8+8+8+1).
		

Crossrefs

Cf. A002376 (least number of positive cubes needed to represent n; differs from this sequence for the first time at n=32, where a(32)=6, while A002376(32)=4).

Programs

  • Haskell
    a055401 n = s n $ reverse $ takeWhile (<= n) $ tail a000578_list where
      s _ []                 = 0
      s m (x:xs) | x > m     = s m xs
                 | otherwise = m' + s r xs where (m',r) = divMod m x
    -- Reinhard Zumkeller, May 08 2011
    
  • Maple
    f:= proc(n,k) local m, j;
    if n = 0 then return 0 fi;
    for j from k by -1 while j^3 > n do od:
    m:= floor(n/j^3);
    m + procname(n-m*j^3, j-1);
    end proc:
    seq(f(n,floor(n^(1/3))),n=0..100); # Robert Israel, Aug 17 2015
  • Mathematica
    a[0] = 0; a[n_] := {n} //. {b___, c_ /; !IntegerQ[c^(1/3)], d___} :> {b, f = Floor[c^(1/3)]^3, c - f, d} // Length; Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Aug 17 2015 *)
  • PARI
    F=vector(30,n,n^3); /* modify to get other sequences of "greedy representations" */
    last_leq(v,F)={local(j=1); while ( F[j]<=v, j+=1 ); F[j-1]} /* Return last element <=v in sorted array F[] */
    greedy(n,F)={local(v=n,ct=0); while ( v, v-=last_leq(v,F); ct+=1; ); ct}
    vector(min(100,F[#F-1]),n,greedy(n,F)) /* show terms */
    /* Joerg Arndt, Apr 08 2011 */
    
  • Scheme
    ;; With memoization-macro definec.
    (definec (A055401 n) (if (zero? n) n (+ 1 (A055401 (A055400 n)))))
    ;; Antti Karttunen, Aug 16 2015

Formula

a(0) = 0; for n >= 1, a(n) = a(n-floor(n^(1/3))^3)+1 = a(A055400(n))+1 = a(n-A048762(n))+1.

Extensions

a(0) = 0 prepended by Antti Karttunen, Aug 16 2015

A007961 n written in base where place values are positive squares.

Original entry on oeis.org

1, 2, 3, 10, 11, 12, 13, 20, 100, 101, 102, 103, 110, 111, 112, 1000, 1001, 1002, 1003, 1010, 1011, 1012, 1013, 1020, 10000, 10001, 10002, 10003, 10010, 10011, 10012, 10013, 10020, 10100, 10101, 100000, 100001, 100002, 100003, 100010, 100011
Offset: 1

Views

Author

R. Muller

Keywords

Comments

For n>1: A000196(n) = number of digits of a(n); A190321(n) = number of nonzero digits of a(n); A053610(n) = sum of digits of a(n). [Reinhard Zumkeller, May 08 2011]

Crossrefs

Programs

  • Haskell
    import Data.Char (intToDigit)
    a007961 :: Integer -> Integer
    a007961 n = read $ map intToDigit $
      t n $ reverse $ takeWhile (<= n) $ tail a000290_list where
        t _ []          = []
        t m (x:xs)
            | x > m     = 0 : t m xs
            | otherwise = (fromInteger m') : t r xs
            where (m',r) = divMod m x
    -- Reinhard Zumkeller, May 08 2011
  • Maple
    A007961 := proc(n)
        local k,nrem,L,b,d;
        k := floor(sqrt(n)) ;
        nrem := n ;
        L := [] ;
        for b from k to 1 by -1 do
            d := floor(nrem/b^2) ;
            L := [d,op(L)] ;
            nrem := nrem -d*b^2 ;
        end do:
        add( op(i,L)*10^(i-1),i=1..nops(L)) ;
    end proc: # R. J. Mathar, Jul 25 2015

A276326 Numbers expressed in greedy A001563-base.

Original entry on oeis.org

0, 1, 2, 3, 10, 11, 12, 13, 20, 21, 22, 23, 30, 31, 32, 33, 40, 41, 100, 101, 102, 103, 110, 111, 112, 113, 120, 121, 122, 123, 130, 131, 132, 133, 140, 141, 200, 201, 202, 203, 210, 211, 212, 213, 220, 221, 222, 223, 230, 231, 232, 233, 240, 241, 300, 301, 302, 303, 310, 311, 312, 313, 320, 321, 322, 323, 330, 331, 332, 333, 340, 341, 400
Offset: 0

Views

Author

Antti Karttunen, Aug 30 2016

Keywords

Comments

Terms A001563(1) = 1, A001563(2) = 4, A001563(3) = 18, ... give the base values for the digit positions from 1 onward. Digit places are filled by always trying to find the largest possible term of A001563 that still fits into the sum.
A130744(8) = 3225600 = 10*A001563(8) is the first number which yields an ambiguous representation when expressed in decimal, because in this base it is actually "A0000000" (where digit "A" stands for ten).

Examples

			To recover n from a(n) the digits in positions i = 1, 2, 3, ... (starting indexing from the least significant digit at right) are multiplied by A001563(i) and added together:
  ----------------
   n         a(n)
  ----------------
   0           0
   1           1
   2           2
   3           3
   4          10
   5          11
   6          12
   7          13
   8          20
   9          21
  10          22
  11          23
  12          30
  13          31
  14          32
  15          33
  16          40
  17          41 (as 4*A001563(2) + 1*A001563(1) = 17)
  18         100 (as 1*A001563(3) + 0*A001563(2) + 0*A001563(1) = 18)
and:
3225599 99111111 (as 3225599 = 9*b(8) + 9*b(7) + b(6) + b(5) + b(4) + b(3) + b(2) + b(1)), where b(n) = A001563(n).
		

Crossrefs

Cf. A276327 (the least significant nonzero digit).
Cf. A276328 (the sum of digits).
Cf. A276333 (the most significant digit).
Cf. A276336 (a largest digit).
Cf. A276337 (number of nonzero digits).
Cf. A033312 (repunits).
Cf. A276091 (no digits larger than one).
Differs from A007090 for the first time at n=16 and from A055655 at n=18.

Programs

  • Mathematica
    f[n_] := Block[{a = {{0, n}}}, Do[AppendTo[a, {First@ #, Last@ #} &@ QuotientRemainder[a[[-1, -1]], (# #!) &[# - i]]], {i, 0, # - 1}] &@ NestWhile[# + 1 &, 0, (# #!) &[# + 1] <= n &]; Rest[a][[All, 1]]]; Table[FromDigits@ f@ n, {n, 72}] (* Michael De Vlieger, Aug 31 2016 *)
  • Scheme
    (define (A276326 n) (let loop ((n n) (s 0)) (if (zero? n) s (let ((dig (A276333 n))) (if (> dig 9) (error "A276326: ambiguous representation of n, digit > 9 would be needed: " n dig) (loop (A276335 n) (+ s (* dig (expt 10 (- (A258198 n) 1))))))))))
Showing 1-4 of 4 results.