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A061742 a(n) is the square of the product of first n primes. 32
1, 4, 36, 900, 44100, 5336100, 901800900, 260620460100, 94083986096100, 49770428644836900, 41856930490307832900, 40224510201185827416900, 55067354465423397733736100, 92568222856376731590410384100, 171158644061440576710668800200900 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Squares of primorials (first definition, A002110).

Exponential superabundant numbers: numbers k with a record value of the exponential abundancy index, A051377(k)/k > A051377(m)/m for all m < k. - Amiram Eldar, Apr 13 2019

Numbers k with a record value of A056170(k), or least number k with A056170(k) = n. - Amiram Eldar, Apr 15 2019

Empirically, these are possibly the denominators for 1 - Sum_{k=1..n} (-1)^(k+1)/prime(k)^2. The numerators are listed in A136370. - Petros Hadjicostas, May 14 2020

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..100

FORMULA

a(n) = Product_{j=1..n} A001248(j). - Alois P. Heinz, May 14 2020

EXAMPLE

a(4) = 2^2 * 3^2 * 5^2 * 7^2 = 44100.

MAPLE

a:= proc(n) option remember; `if`(n=0, 1, ithprime(n)^2*a(n-1)) end:

seq(a(n), n=0..15);  # Alois P. Heinz, May 14 2020

MATHEMATICA

a[n_]:=Product[Prime[i]^2, {i, 1, n}]; (* Vladimir Joseph Stephan Orlovsky, Dec 05 2008 *)

PROG

(PARI) for(n=0, 20, print1(prod(k=1, n, prime(k)^2), ", "))

(PARI) { n=-1; m=1; forprime (p=2, prime(101), write("b061742.txt", n++, " ", m^2); m*=p ) } \\ Harry J. Smith, Jul 27 2009

(MAGMA) [n eq 0 select 1 else (&*[NthPrime(j)^2: j in [1..n]]): n in [0..20]]; // G. C. Greubel, Apr 19 2019

(Sage) [product(nth_prime(j)^2 for j in (1..n)) for n in (0..20)] # G. C. Greubel, Apr 19 2019

CROSSREFS

Equals A002110^2.

Cf. A001248, A051377, A056170, A129575, A136370, A322887.

Sequence in context: A009446 A134052 A127901 * A136469 A120605 A337851

Adjacent sequences:  A061739 A061740 A061741 * A061743 A061744 A061745

KEYWORD

nonn

AUTHOR

Jason Earls, Jun 21 2001

STATUS

approved

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Last modified September 22 19:36 EDT 2021. Contains 347608 sequences. (Running on oeis4.)