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.

A027570 Initial members of prime decaplets (p, p+2, p+6, p+12, p+14, p+20, p+24, p+26, p+30, p+32).

Original entry on oeis.org

9853497737, 21956291867, 22741837817, 164444511587, 179590045487, 217999764107, 231255798857, 242360943257, 666413245007, 696391309697, 867132039857, 974275568237, 976136848847, 1002263588297, 1086344116367
Offset: 1

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All terms are congruent to 167 (modulo 210). - Matt C. Anderson, May 29 2015

Crossrefs

Programs

  • Maple
    a := 1:
    for b to 25 do
    a := a*ithprime(b):
    end do:
    a;
    # now 'a' is the product of the primes less than 100.
    composite_small := proc (n::integer)
    description "procedure to determine if n has a prime factor less than 100";
    if igcd(2305567963945518424753102147331756070, n) = 1 then return false
    else return true;
    end if;
    end proc:
    # so composite_small tests if there are any factors 2 through 97.
    #begin initialization section
    p := [0, 2, 6, 12, 14, 20, 24, 26, 30, 32];
    o := [7517, 10247, 12137, 14447, 14867, 17177, 21377, 24107, 25997, 28727];
    m := 30030;
    #end initialization section
    # implement isprime(m*n+o+p)
    with(ArrayTools):
    os:=Size(o,2):
    ps:=Size(p,2):
    #here ps is 10 so a prime constellation of length 10.
    loopstop := 10^11:
    loopstart := 0:
    for n from loopstart to loopstop do
    for a to os do
    counter := 0; wc := 0; wd := 0;
      while `and`(wd > -10, wd < ps) do
      wd := wd+1;
      if composite_small(m*n+o[a]+p[wd]) = false then wd := wd+1
      else wd := -10 end if;
      end do;
    if wd >= 9 then
    while `and`(counter >= 0, wc < ps) do
      wc := wc+1;
      if isprime(m*n+o[a]+p[wc]) then counter := counter+1;
      else counter := -1
      end if;
    end do;
    end if;
    if counter = ps then print(m*n+o[a]) end if;
    end do:
    end do:
    # Matt C. Anderson, Apr 15 2015
  • Perl
    use ntheory ":all"; say for sieve_prime_cluster(1,1e13, 2,6,12,14,20,24,26,30,32); # Dana Jacobsen, Sep 30 2015