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.

A061214 Product of composite numbers between the n-th and (n+1)st primes.

Original entry on oeis.org

1, 4, 6, 720, 12, 3360, 18, 9240, 11793600, 30, 45239040, 59280, 42, 91080, 311875200, 549853920, 60, 1072431360, 328440, 72, 2533330800, 531360, 4701090240, 60072730099200, 970200, 102, 1157520, 108, 1367520, 1063186156509747740870400000, 2146560, 43191973440
Offset: 1

Views

Author

Amarnath Murthy, Apr 21 2001

Keywords

Examples

			a(4) = 8 * 9 * 10 = 720. 7 is the fourth prime and 11 is the fifth prime. a(5) = 12 as 11 and 13 both are primes.
		

Crossrefs

Cf. A046933 and A054265 (number and sum of these composites).

Programs

  • Haskell
    a061214 n = a061214_list !! (n-1)
    a061214_list = f a000040_list where
       f (p:ps'@(p':ps)) = (product [p+1..p'-1]) : f ps'
    -- Reinhard Zumkeller, Jun 22 2011
    
  • Maple
    A061214 := proc(n)
        local k ;
        product(k,k=ithprime(n)+1..ithprime(n+1)-1) ;
    end proc: # R. J. Mathar, Apr 23 2013
  • Mathematica
    Table[Times@@Range[Prime[n]+1,Prime[n+1]-1],{n,30}] (* Harvey P. Dale, Jun 14 2011 *)
    Times@@Range[#[[1]]+1,#[[2]]-1]&/@Partition[Prime[Range[40]],2,1] (* Harvey P. Dale, Apr 23 2022 *)
  • PARI
    { n=0; q=2; forprime (p=3, prime(2001), a=1; for (i=q + 1, p - 1, a*=i); q=p; write("b061214.txt", n++, " ", a) ) } \\ Harry J. Smith, Jul 19 2009
    
  • PARI
    v=primes(100);for(i=1,#v-1,v[i]=prod(j=v[i]+1,v[i+1]-1,j));vecextract(v,"1..-2") \\ Charles R Greathouse IV, Feb 27 2012
    
  • Python
    from math import prod
    from sympy import prime
    def A061214(n): return prod(i for i in range(prime(n)+1,prime(n+1))) # Chai Wah Wu, Jul 10 2022

Formula

A006530(a(n)) = A052248(n) for n > 1. - Reinhard Zumkeller, Jun 22 2011

Extensions

More terms from James Sellers, Apr 24 2001
Better definition from T. D. Noe, Jan 21 2008

A072472 a(n) = product of numbers from prime(n)+1 up to prime(n+1), where prime(n) is the n-th prime.

Original entry on oeis.org

3, 20, 42, 7920, 156, 57120, 342, 212520, 342014400, 930, 1673844480, 2430480, 1806, 4280760, 16529385600, 32441381280, 3660, 71852901120, 23319240, 5256, 200133133200, 44102880, 418397031360, 5827054819622400, 97990200, 10506, 123854640, 11772, 154529760
Offset: 1

Views

Author

Amarnath Murthy, Jun 20 2002

Keywords

Comments

Originally the offset was -1 and two terms more in front were pre defined in a inscrutable manner (a(-1)=1, a(0) = 2; .....). - Karl-Heinz Hofmann, Apr 18 2023

Examples

			a(1) = 3
a(2) = 4 * 5 = 20
a(3) = 6 * 7 = 42
a(4) = 8 * 9 * 10 * 11 = 7920
		

Crossrefs

Programs

  • Mathematica
    a[n_] := Product[k, {k, Prime[n] + 1, Prime[n + 1]}]; Table[a[n], {n, 1, 30}]
  • PARI
    a(n) = prod(k=prime(n)+1, prime(n+1), k); \\ Michel Marcus, Apr 17 2023
  • Python
    from sympy import prod, sieve as prime
    def A072472(n):
        return prod(range(prime[n]+1, prime[n+1]+1)) # Karl-Heinz Hofmann, Apr 17 2023
    

Formula

a(n) = A000040(n+1)*A061214(n). - Karl-Heinz Hofmann, Apr 18 2023

Extensions

Edited by Robert G. Wilson v, Jun 21 2002
Offset, data and name corrected by Karl-Heinz Hofmann, Apr 18 2023

A361760 a(n) = Product_{i=prime(n)..prime(n+1)-1} i.

Original entry on oeis.org

2, 12, 30, 5040, 132, 43680, 306, 175560, 271252800, 870, 1402410240, 2193360, 1722, 3916440, 14658134400, 29142257760, 3540, 65418312960, 22005480, 5112, 184933148400, 41977440, 390190489920, 5346472978828800, 94109400, 10302, 119224560, 11556, 149059680, 120140035685601494718355200000, 272613120
Offset: 1

Views

Author

Karl-Heinz Hofmann, Mar 23 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = my(x=1); for(i=prime(n), prime(n+1)-1, x*=i); x; \\ Michel Marcus, Mar 28 2023
  • Python
    from sympy import prod, sieve
    def A361760(n): return prod(range(sieve[n], sieve[n+1]))
    

Formula

a(n) = A000040(n)*A061214(n).
Showing 1-3 of 3 results.