1537381

Appears in sequences

• Triangular numbers such that both the number formed by the first floor((k+1)/2) digits and the remaining part (if any) are triangular numbers, where k is the number of digits.at n=26A068821
• Numbers of the form p*q, p and q prime with q=2*p-1.at n=31A129521
• Poulet numbers (2-pseudoprimes) of the form 7200*n^2 + 8820*n + 2701.at n=8A214016
• Squarefree numbers (from A005117) with prime divisors in a 2p-1 progression.at n=33A231814
• Record values in A265388.at n=34A265395
• Fermat pseudoprimes to base 2 that are triangular.at n=25A293622
• Fermat pseudoprimes to base 2 that are hexagonal.at n=24A322130
• Odd numbers > 1, not powers of primes, for which A326147(n) is equal to abs(A326146(n)).at n=41A326148
• Numbers that are super pseudoprimes to both bases 2 and 3.at n=15A333130
• Record values in A346599.at n=37A346601
• Triangular numbers that are emirpimes.at n=27A375385