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 A137727 Final digit of prime(n)*prime(n+1). 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is 1, 3, 7, or 9 for n > 3. I conjecture that 1 and 9 appear 17/66 of the time and 3 and 7 appear 8/33 of the time. - Charles R Greathouse IV, Jan 03 2013 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A010879(A006094(n)). - Felix FrÃ¶hlich, Jun 05 2021 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 *) PROG (PARI) a(n)=prime(n)*prime(n+1)%10 \\ Charles R Greathouse IV, Dec 29 2012 (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 (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 CROSSREFS Cf. A006094 (Products of 2 successive primes), A007652 (Final digit of prime(n)), A010879 (final digit of n), A110923 (final two digits of prime(n) (with leading zero omitted)), A137728 (second digit from the end of product of first n primes). Sequence in context: A199600 A021608 A108088 * A010497 A167918 A070860 Adjacent sequences:  A137724 A137725 A137726 * A137728 A137729 A137730 KEYWORD nonn,base AUTHOR Alexander Adamchuk, Feb 08 2008 STATUS approved

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Last modified November 28 16:21 EST 2021. Contains 349413 sequences. (Running on oeis4.)