login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A173176 Greater twin primes in A172240. 4
7, 13, 19, 31, 43, 61, 73, 103, 109, 139, 151, 181, 193, 199, 229, 241, 271, 283, 313, 349, 421, 433, 463, 523, 571, 601, 619, 643, 661, 811, 823, 829, 859, 883, 1021, 1033, 1051, 1063, 1093, 1153, 1231, 1279, 1291, 1303, 1321, 1429, 1453, 1483, 1489, 1609, 1621, 1669, 1699, 1723, 1789, 1873, 1879, 1933, 1951, 1999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For a(n) > 5, first difference of the sequence is divisible by 6. (Conjectured or proved?)

Also for a(n)>5, a(n)-1 is divisible by 6, if a(n)-2 is prime p such that p+1 is divisible by 6.

LINKS

Table of n, a(n) for n=1..60.

FORMULA

A172240 INTERSECT A006512.

MAPLE

isA006512 := proc(p) isprime(p) and isprime(p-2) ; end proc:

isA000430 := proc(p) if isprime(p) then true; else if issqr(p) then isprime(sqrt(p)) ; else false; end if; end if; end proc:

isA181602 := proc(p) if isprime(p) then if numtheory[bigomega](p-1) =2 and  isA000430(p+2) then true; else false; end if; else false;   end if ; end proc:

isA181669 := proc(p) isA181602(p) and (p mod 6)= 5 ; end proc:

isA172240 := proc(n) isprime(n) and not isA181669(n) ; end proc:

isA173176 := proc(n) isA172240(n) and isA006512(n) ; end proc:

for n from 2 to 2000 do if isA173176(n) then printf("%d, ", n) ; end if; end do:

CROSSREFS

Cf. A172487, A181669, A181602.

Sequence in context: A053458 A040058 A172057 * A216550 A267803 A240971

Adjacent sequences:  A173173 A173174 A173175 * A173177 A173178 A173179

KEYWORD

nonn,easy

AUTHOR

Giovanni Teofilatto, Nov 22 2010

EXTENSIONS

Corrected by R. J. Mathar, Dec 01 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 22 16:37 EST 2020. Contains 331152 sequences. (Running on oeis4.)