A274363 Numbers n such that n and n+1 both have 26 divisors.

689278976, 38492803071, 100821266432, 147331919871, 421606494207, 560920563711, 732088143872, 753855967232, 918212890624, 1218308829183, 1414219239423, 1485254832128, 1544826179583, 1566594002943, 1671079555071, 1675433119743, 1681165242368

Offset: 1

Author

Charles R Greathouse IV, Jun 19 2016

Keywords

• nonn

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A005237 and A137489.

Programs

PARI

is(n)=numdiv(n)==26 && numdiv(n+1)==26

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
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)