157641

Appears in sequences

• Doubly triangular numbers: a(n) = n*(n+1)*(n^2+n+2)/8.at n=33A002817
• Smith numbers which are also base-2 pseudoprimes.at n=5A063844
• Smith triangular numbers.at n=21A098840
• Pseudoquadprimes: p+4 for primes p where p+4 divides p^(p+4) + 4 and p+4 is composite.at n=18A100875
• Concatenation of triangular number k and its 10's complement is prime.at n=29A108970
• Pseudoprimes (base-2) equal to product of 4 primes not necessarily distinct.at n=14A112441
• Numbers m such that exactly half of the a such that 0<a<m and (a,m)=1 satisfy a^(m-1) == 1 (mod m).at n=27A191311
• Numbers in A191311 but not in A129521.at n=13A191592
• Pseudoprimes divisible by a smaller pseudoprime.at n=11A215150
• Pseudoprimes n to base 2 such that n-2 and n-4 are primes.at n=3A230488
• Fermat pseudoprimes to base 2 that are triangular.at n=12A293622
• Fermat pseudoprimes to base 2 that are hexagonal.at n=11A322130
• Terms of A324315 (squarefree integers m > 1 such that if prime p divides m, then the sum of the base p digits of m is at least p) that are also hexagonal numbers (A000384) with index equal to their largest prime factor.at n=14A324319
• Expansion of e.g.f.: exp(x / (1-x)^x).at n=8A347726