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.

A019506 Hoax numbers: composite numbers whose digit-sum equals the sum of the digit-sums of its distinct prime factors.

Original entry on oeis.org

22, 58, 84, 85, 94, 136, 160, 166, 202, 234, 250, 265, 274, 308, 319, 336, 346, 355, 361, 364, 382, 391, 424, 438, 454, 456, 476, 483, 516, 517, 526, 535, 562, 627, 634, 644, 645, 650, 654, 660, 663, 690, 702, 706, 732, 735, 762, 778, 855, 860
Offset: 1

Views

Author

Mario Velucchi (mathchess(AT)velucchi.it)

Keywords

Examples

			22 = 2*11 and digit-sum(22) = 4 = digit-sum(2) + digit-sum(11).

Links

Crossrefs

Cf. A006753.
Cf. A002808, A027748, A001221, A007953, A050223, A202393, A202387.

Programs

  • Haskell
    a019506 n = a019506_list !! (n-1)
a019506_list = [x | x <- a002808_list,
                    a007953 x == sum (map a007953 (a027748_row x))]
-- Reinhard Zumkeller, Dec 19 2011
  • Mathematica
    Select[Range[2,1000],!PrimeQ[#]&&Total[Flatten[IntegerDigits/@ Transpose[ FactorInteger[#]][[1]]]]==Total[IntegerDigits[#]]&] (* Harvey P. Dale, Feb 24 2013 *)
  • PARI
    isok(m) = !isprime(m) && (sumdigits(m) == vecsum(apply(sumdigits, factor(m)[,1]))); \\ Michel Marcus, Feb 03 2022

Formula

A007953(a(n)) = sum(A007953(A027748(a(n),k)): k=1..A001221(a(n))) and A066247(a(n)) = 1. [Reinhard Zumkeller, Dec 19 2011]

A050218 Sums of digits of Smith numbers A006753.

Original entry on oeis.org

4, 4, 9, 13, 13, 13, 4, 13, 4, 13, 13, 13, 13, 13, 18, 13, 13, 15, 13, 15, 13, 13, 13, 13, 18, 21, 15, 13, 15, 15, 18, 15, 15, 18, 15, 13, 17, 18, 15, 22, 15, 15, 15, 22, 13, 15, 13, 22, 22, 15, 4, 13, 13, 13, 13, 15, 17, 18, 13, 15, 15, 13, 13, 22, 17, 18, 21, 22, 13, 15
Offset: 1

Views

Author

Eric W. Weisstein

Keywords

Links

Crossrefs

Cf. A006753, A050219, A050220.
Cf. A202388, A050223.

Programs

  • Mathematica
    d[n_]:=IntegerDigits[n]; tr[n_]:=Transpose[FactorInteger[n]]; t={}; Do[If[!PrimeQ[n]&&(x=Total[d[n]])==Total[d@tr[n][[1]]*tr[n][[2]],2],AppendTo[t,x]],{n,4,1850}]; t (* Jayanta Basu, Jun 04 2013 *)

Formula

a(n) = A007953(A006753(n)).

Extensions

Offset corrected by Reinhard Zumkeller, Dec 19 2011

A202393 Digital root of Hoax Numbers A019506.

Original entry on oeis.org

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

Views

Author

Reinhard Zumkeller, Dec 19 2011

Keywords

Links

Crossrefs

Cf. A050223, A202388.

Formula

a(n) = A010888(A019506(n)).
Showing 1-3 of 3 results.

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

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