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A055738 Number of prime quadruples < 10^n, where a prime quadruple means 4 successive primes {p, p', p'', p'''} with p''' = p + 8. 1
0, 3, 6, 13, 39, 167, 900, 4769, 28389, 180530, 1209319, 8398279, 60070591, 441296837, 3314576488 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
REFERENCES
J. Recreational Math., vol. 23, No. 2, 1991, p. 97.
LINKS
EXAMPLE
For n=2 the quadruples are 3,5,7,11; 5,7,11,13; 11,13,17,19.
MAPLE
with(numtheory): x := 1229; t1 := [seq(ithprime(i), i=1..x)]; c := 0: for i from 1 to x-3 do if t1[i]+8 = t1[i+3] then c := c+1; fi; od: c; # the values of x to use are given by A006880.
MATHEMATICA
x=168; a=Table[ Prime[ n ], {n, 1, x} ]; c=0; Do[ If[ a[ [ n ] ]+8==a[ [ n+2 ] ], c++ ], {n, 1, x-3} ]; # the values of x to use are given by A006880.
CROSSREFS
Sequence in context: A036781 A370208 A084816 * A301656 A359669 A322183
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Jun 09 2000
EXTENSIONS
a(8)-a(9) from Jud McCranie, Oct 08 2000.
a(10)-a(12) from Bert Dobbelaere, Apr 17 2019
a(13)-a(15) from Charles R Greathouse IV, Feb 12 2022
STATUS
approved

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Last modified July 17 22:12 EDT 2024. Contains 374377 sequences. (Running on oeis4.)