22791

Appears in sequences

• Pseudoprimes to base 5.at n=32A005936
• Pseudoprimes to base 17.at n=42A020145
• Strong pseudoprimes to base 17.at n=15A020243
• Strong pseudoprimes to base 25.at n=17A020251
• Strong pseudoprimes to base 76.at n=19A020302
• a(n) = 49*(n*(n+1)/2) + 6.at n=30A061792
• Triangular numbers with sum of digits = 21.at n=17A068131
• Triangular numbers which are also happy numbers (cf. A007770).at n=33A076712
• Triangular numbers m such that A040115(m) is also triangular.at n=23A087597
• Numbers m such that all terms in the sequence m, A040115(m), A040115(A040115(m)), ..., 0 are triangular numbers (A000217).at n=18A087598
• Nonprime numbers n such that phi(n) divides n^2 - 1, where phi(n) (A000010) is Euler's totient function.at n=17A098271
• Concatenation of triangular number k and its 10's complement is prime.at n=14A108970
• Triangular numbers equal to the sum of a prime number with its index.at n=18A115886
• Triangular numbers for which the sum of the digits is an octagonal number.at n=20A117523
• Hexagonal numbers with prime indices.at n=27A117961
• Numbers which are both lucky and triangular.at n=39A118565
• Least power of 3 having exactly n consecutive 2's in its decimal representation.at n=8A131551
• Triangular numbers n*(n+1)/2 with n and n+1 composite, where number of prime factors in n = number of prime factors in n+1. (Prime factors are counted with multiplicity.)at n=37A144486
• Terms of A122782 which are not Carmichael numbers A002997.at n=41A153515
• a(n) is the smallest m for which 3^m contains n consecutive identical digits.at n=8A215727