A137727 Final digit of prime(n)*prime(n+1).
6, 5, 5, 7, 3, 1, 3, 7, 7, 9, 7, 7, 3, 1, 1, 7, 9, 7, 7, 3, 7, 7, 7, 3, 7, 3, 1, 3, 7, 1, 7, 7, 3, 1, 9, 7, 1, 1, 1, 7, 9, 1, 3, 1, 3, 9, 3, 1, 3, 7, 7, 9, 1, 7, 1, 7, 9, 7, 7, 3, 9, 1, 7, 3, 1, 7, 7, 9, 3, 7, 7, 3, 1, 7, 7, 7, 3, 7, 9, 1, 9, 1, 3, 7, 7, 7, 3, 7, 3, 1, 3, 3, 7, 9, 7, 7, 9, 3, 3, 7, 9, 1, 7, 9, 7
Offset: 1
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
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Mathematica
Table[ Mod[ Prime[n]*Prime[n+1], 10 ], {n,1,1000} ] Mod[Times@@@Partition[Prime[Range[110]],2,1],10] (* Harvey P. Dale, Oct 05 2014 *) -
PARI
a(n)=prime(n)*prime(n+1)%10 \\ Charles R Greathouse IV, Dec 29 2012
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Python
from sympy import prime def a(n): return (prime(n)*prime(n+1))%10 print([a(n) for n in range(1, 106)]) # Michael S. Branicky, Jun 05 2021
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Python
# much faster alternate for initial segment of sequence from sympy import nextprime def aupton(terms): p1, p2, alst = 2, 3, [] while len(alst) < terms: p1, p2, alst = p2, nextprime(p2), alst + [(p1*p2)%10] return alst print(aupton(105)) # Michael S. Branicky, Jun 05 2021
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