102831

Appears in sequences

• Strong pseudoprimes to base 19.at n=34A020245
• a(1) = 0, then smallest triangular number such that a(n+1)- a(n) is a palindrome.at n=30A075057
• Concatenation of triangular number k and its 10's complement is prime.at n=26A108970
• Hexagonal numbers for which both the sum of the digits and the product of the digits are also hexagonal numbers.at n=21A117064
• Triangular numbers T such that T+10 is the next prime after T.at n=16A129540
• a(n) = m*(m+1)/2, where m = floor(n^(3/2)).at n=58A185541
• Number of n X 2 0,1 arrays indicating 2 X 2 subblocks of some larger (n+1) X 3 binary array having a sum of one or less, with rows and columns of the latter in lexicographically nondecreasing order.at n=39A227161
• The first of two consecutive triangular numbers the sum of which is equal to the sum of two consecutive prime numbers.at n=28A298462
• Triangular numbers that are the sum of two distinct nonzero triangular numbers in exactly two ways.at n=21A350368
• Hexagonal numbers that are sphenic numbers.at n=43A380007