

A055738


Number of prime quadruples < 10^n, where a prime quadruple means 4 successive primes {p, p', p'', p'''} with p''' = p + 8.


1




OFFSET

1,2


REFERENCES

J. Recreational Math., vol. 23, No. 2, 1991, p. 97.


LINKS

Table of n, a(n) for n=1..9.
Index entries for sequences related to numbers of primes in various ranges


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 x3 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, x3} ]; # the values of x to use are given by A006880.


CROSSREFS

Cf. A055737, A006880.
Sequence in context: A216999 A036781 A084816 * A137584 A053365 A101034
Adjacent sequences: A055735 A055736 A055737 * A055739 A055740 A055741


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jun 09 2000


EXTENSIONS

2 more terms from Jud McCranie, Oct 08 2000.


STATUS

approved



