A274363 - OEIS

%I #9 Jul 08 2016 00:15:12

%S 689278976,38492803071,100821266432,147331919871,421606494207,

%T 560920563711,732088143872,753855967232,918212890624,1218308829183,

%U 1414219239423,1485254832128,1544826179583,1566594002943,1671079555071,1675433119743,1681165242368

%N Numbers n such that n and n+1 both have 26 divisors.

%H Charles R Greathouse IV, <a href="/A274363/b274363.txt">Table of n, a(n) for n = 1..10000</a>

%o (PARI) is(n)=numdiv(n)==26 && numdiv(n+1)==26

%o (PARI) has(n)=if(n%4==2,ispower(n/2,12,&n) && isprime(n), bitand(n,8191)==4096 && isprime(n>>12) && n>8192) \\ check if n is even with 26 divisors

%o list(lim)=my(v=List(),t); forprime(p=2,sqrtnint(lim\=1,25), t=p^25; if(has(t+1), listput(v,t)); if(has(t-1), listput(v,t-1))); forprime(p=3,sqrtnint(lim\3,12), my(p12=p^12); forprime(q=3,lim\p12, if(p==q,next); t=p12*q; if(has(t+1), listput(v,t)); if(has(t-1), listput(v,t-1)))); Set(v)

%Y Intersection of A005237 and A137489.

%K nonn

%O 1,1

%A _Charles R Greathouse IV_, Jun 19 2016