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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A276155 Complement of A276154; numbers that cannot be obtained by shifting left the primorial base representation (A049345) of some number.

Original entry on oeis.org

1, 3, 4, 5, 7, 9, 10, 11, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 33, 34, 35, 37, 39, 40, 41, 43, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 63, 64, 65, 67, 69, 70, 71, 73, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 91, 93, 94, 95, 97, 99, 100, 101, 103, 105, 106, 107, 108, 109
Offset: 1

Views

Author

Antti Karttunen, Aug 24 2016

Keywords

Comments

The first 25 terms, when viewed in primorial base (A049345) look as: 1, 11, 20, 21, 101, 111, 120, 121, 201, 211, 220, 221, 300, 301, 310, 311, 320, 321, 400, 401, 410, 411, 420, 421, 1001.

Crossrefs

Complement: A276154.
Row 1 of A276943 and A286623. Column 1 of A276945 and A286625.
Cf. A005408, A057588, A061720, A143293, A286630 (subsequences).
For the first 17 terms coincides with A273670.

Programs

  • Mathematica
    nn = 109; b = MixedRadix[Reverse@ Prime@ NestWhileList[# + 1 &, 1, Times @@ Prime@ Range[# + 1] <= nn &]]; Complement[Range@ nn, Table[FromDigits[#, b] &@ Append[IntegerDigits[n, b], 0], {n, 0, nn}]] (* Version 10.2, or *)
    nn = 109; f[n_] := Block[{a = {{0, n}}}, Do[AppendTo[a, {First@ #, Last@ #} &@ QuotientRemainder[a[[-1, -1]], Times @@ Prime@ Range[# - i]]], {i, 0, #}] &@ NestWhile[# + 1 &, 0, Times @@ Prime@ Range[# + 1] <= n &]; Rest[a][[All, 1]]]; Complement[Range@ nn, Table[Total[Times @@@ Transpose@ {Map[Times @@ # &, Prime@ Range@ Range[0, Length@ # - 1]], Reverse@ #}] &@ Append[f@ n, 0], {n, 0, nn}]] (* Michael De Vlieger, Aug 26 2016 *)

A286629 a(n) = (A000040(n)-1) * A002110(n).

Original entry on oeis.org

2, 12, 120, 1260, 23100, 360360, 8168160, 174594420, 4908043140, 181151410440, 6016814703900, 267146572853160, 12170010541088400, 549475975930141260, 28284929999070604860, 1694636240813882325960, 111520100308944333066060, 7037302881564418258996200, 518649222371297625688019940, 39055858108868927267719077300
Offset: 1

Views

Author

Antti Karttunen, Jul 07 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(Prime[n] - 1) Product[Prime[k], {k, n}], {n, 100}] (* Indranil Ghosh, Jul 07 2017 *)
  • PARI
    a(n) = (prime(n)-1)*prod(k=1, n, prime(k)); \\ Michel Marcus, Jul 07 2017
  • Python
    from sympy import prime, primorial
    def a002110(n): return 1 if n<1 else primorial(n)
    def a(n): return (prime(n) - 1)*a002110(n)
    print([a(n) for n in range(1, 21)]) # Indranil Ghosh, Jul 07 2017
    
  • Scheme
    (define (A286629 n) (* (- (A000040 n) 1) (A002110 n)))
    

Formula

a(n) = A006093(n) * A002110(n) = (A000040(n)-1) * A002110(n).
a(n) = A286630(n) - A002110(n).
a(n) = A276154(A061720(n-1)).
Showing 1-2 of 2 results.