51040

Appears in sequences

• Triangular numbers with sum of digits = 10.at n=31A068129
• Triangular numbers whose digit permutations yield at least two further triangular numbers.at n=29A069674
• Triangular numbers whose sum of prime factors (with repetition) is also triangular.at n=27A076169
• Triangular numbers which are 8-almost primes.at n=6A076582
• Triangular numbers > 0 with a prime signature that has not occurred earlier.at n=34A085076
• Triangular numbers in which the sum of the external digits equals the sum of the internal digits.at n=16A088289
• a(0)=0; a(1)=1; a(n) = triangular number at index 5*2^(n-2)-1.at n=8A141499
• a(n) = number of terms in A213717 whose magnitude is in range [(2^n)-1,(2^(n+1))-2] (or equally, in range [(2^n),(2^(n+1))-1]).at n=17A213722
• Number of permutations p of {1..2n} such that p[2k-1]<p[2k] <=> p[2k]<p[2k+1].at n=4A261683
• Array read by antidiagonals: T(m,n) (m>=1, n>=1) = number of m X n whirlpool permutations.at n=16A334518
• Array read by antidiagonals: T(m,n) (m>=1, n>=1) = number of m X n whirlpool permutations.at n=19A334518
• Triangle read by rows: T(n,k) (1<=k<=n) = number of n X k whirlpool permutations (see A334518).at n=11A334519
• Numbers that start a run of four consecutive triangular numbers with four distinct prime factors.at n=9A349773