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.

A071367 Numbers n such that n+0, n+1, n+2, n+3 and n+4 are, in some order, 1 * a prime, 2 * a prime, 3 * a prime, 4 * a prime and 5 * a prime.

Original entry on oeis.org

6, 211, 2305, 2731, 19441, 116131, 174595, 222931, 229945, 232051, 243091, 266401, 334315, 350785, 423481, 495265, 523945, 530545, 535915, 539401, 556705, 600601, 663601, 671035, 689131, 721891, 907195, 908041, 1105105, 1113961, 1289731
Offset: 1

Views

Author

Don Reble, May 21 2002

Keywords

Comments

A001221(a(n)) <= 2; A001222(a(n)) <= 3. - Reinhard Zumkeller, Aug 01 2015

Examples

			211 is a term because 211=1*211, 212=4*53, 213=3*71, 214=2*107 and 215=5*43. The left factors are the integers 1 to 5; and the right factors are primes.
6 is a term because 6=2*3, 7=1*7, 8=4*2, 9=3*3, 10=5*2 where the left factors are the integers 1 to 5 and the right factors are primes. - _Sean A. Irvine_, Jul 14 2024
		

Crossrefs

Programs

  • Haskell
    a071367 n = a071367_list !! (n-1)
    a071367_list = tail $ filter f [1..] where
       f x = and $ map g [5, 4 .. 1] where
         g k = sum (map h $ map (+ x) [0..4]) == 1 where
           h z = if r == 0 then a010051' z' else 0
                 where (z', r) = divMod z k
    -- Reinhard Zumkeller, Jul 31 2015

Extensions

Missing 6 inserted by Sean A. Irvine, Jul 14 2024