108811

Appears in sequences

• Lexicographically earliest sequence of pairwise coprime triangular numbers.at n=21A034792
• Triangular numbers whose reverse is prime.at n=22A066751
• Triangular numbers which are the product of two primes.at n=28A068443
• Triangular numbers which are one more than a product of distinct triangular numbers.at n=35A083517
• Triangular numbers whose sum of aliquot divisors is a prime number.at n=35A083676
• Triangular numbers that are also brilliant (A078972).at n=21A113940
• Triangular numbers whose digit reversal is prime; trailing zeros are permitted.at n=29A115704
• Triangular numbers composed of digits {0,1,8}.at n=6A119045
• Semiprimes in A006987(n), or semiprime binomial coefficients: C(n,k), 2 <= k <= n-2.at n=29A124000
• Triangular numbers T such that T+10 is the next prime after T.at n=18A129540
• Product p*q of two primes with q = 2*p + 1.at n=15A156592
• Number of (n+2) X 5 binary arrays with each 3 X 3 subblock having rows and columns in lexicographically nondecreasing order.at n=20A184542
• a(n) = Fibonacci(n) * (2*Fibonacci(n) + 1).at n=13A229912
• Numbers n such that A229964(n) = 1.at n=18A229965
• Squarefree numbers (from A005117) with prime divisors in a 2p+1 progression.at n=20A231966
• Triangular numbers n such that each decimal digit of n is equal to the difference of at least two other digits of n.at n=16A255917
• Numbers n with the property that the symmetric representation of sigma(n) has four parts, each of width one and two regions meet at the center of the Dyck path.at n=25A264104
• a(n) = A000217(A000217(n)+1).at n=30A267707