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.

A160669 Smallest prime divisor of A160668(n).

Original entry on oeis.org

2, 7, 5, 3, 89, 3, 83, 3, 7, 71, 3, 3, 59, 3, 53, 47, 41, 3, 3, 29, 3, 3, 17, 11, 3, 29, 3, 19, 3, 587, 3, 11, 863, 3, 23, 3, 3, 3, 7, 827, 821, 3, 809, 3, 11, 3, 3, 3, 773, 3, 13, 761, 3, 7, 743, 11, 17, 3, 3, 719, 3, 7, 3, 13, 3, 683, 3, 3, 653, 3, 647, 641, 3, 3, 3, 617, 13, 3, 599
Offset: 1

Views

Author

Enoch Haga, May 23 2009

Keywords

Examples

			a(1)=2 because in A160668 a(1)=8, so the first prime divisor is 2.

Crossrefs

Cf. A160668 A160670

Programs

  • UBASIC
    10 'recipseq, Enoch Haga, May 22 2009 20 N=3:print N:C=2 30 A=3:S=sqrt(N) 40 B=N/A 50 if A*B=int(N) then 70 60 A=A+2:if A

A228628 9's complement of prime(n).

Original entry on oeis.org

7, 6, 4, 2, 88, 86, 82, 80, 76, 70, 68, 62, 58, 56, 52, 46, 40, 38, 32, 28, 26, 20, 16, 10, 2, 898, 896, 892, 890, 886, 872, 868, 862, 860, 850, 848, 842, 836, 832, 826, 820, 818, 808, 806, 802, 800, 788, 776, 772, 770, 766, 760, 758, 748, 742, 736, 730, 728
Offset: 1

Views

Author

Michel Lagneau, Aug 28 2013

Keywords

Comments

a(n) = 10^k - 1 - prime(n) where k is the number of digits in prime(n). If d is d digit in prime(n) replace it with 9 - d.

Examples

			a(6) = 86 because prime(6) = 13 and 9 - 1 = 8, 9 - 6 = 3.

Links

Crossrefs

Cf. A000040, A061601, A160668.

Programs

  • Maple
    a:= n-> (p-> 10^length(p)-p-1)(ithprime(n)):
seq(a(n), n=1..100);  # Alois P. Heinz, Dec 08 2017
  • Mathematica
    nineComplement[n_] := FromDigits[Table[9, {Length[IntegerDigits[Prime[n]]]}] - IntegerDigits[Prime[n]]]; Table[nineComplement[n], {n, 1, 71}]
  • PARI
    a(n)=my(p=prime(n));10^#Str(p)-p-1 \\ Charles R Greathouse IV, Aug 29 2013
  • Python
    from sympy import primerange
def nc(n): return 10**len(str(n)) - 1 - n
def auptop(limit): return [nc(p) for p in primerange(1, limit+1)]
print(auptop(271)) # Michael S. Branicky, Jul 06 2021

Formula

a(n) = A061601(A000040(n)). - Charles R Greathouse IV, Aug 29 2013
a(n) = A160668(n) - 1. Alois P. Heinz, Dec 08 2017

A160670 Duplicate of A145985.

Original entry on oeis.org

7, 5, 3, 89, 83, 71, 59, 53, 47, 41, 29, 17, 11, 3, 887, 863, 827, 821, 809, 773, 761, 743, 719, 683, 653, 647, 641, 617, 599, 569, 557, 521, 509, 491, 479, 443, 431, 401, 383, 359, 353, 347, 317, 281, 257, 239, 227, 191, 179, 173, 137, 113, 89, 71, 59, 53, 47, 29
Offset: 1

Views

Author

Enoch Haga, May 23 2009

Keywords

Comments

Previous name was: Primes in A160668 in order of appearance.

Crossrefs

Cf. A160668, A160669.

Programs

  • UBASIC
    10 'recipseq, Enoch Haga, May 22 2009
20 N=3:print N:C=2
30 A=3:S=sqrt(N)
40 B=N/A
50 if A*B=int(N) then 70
60 A=A+2:if A
Showing 1-3 of 3 results.

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

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