105570

Appears in sequences

• Numbers n such that sopf(n) = sopf(n+1) - sopf(n-1), where sopf(x) = sum of the distinct prime factors of x.at n=17A076525
• Triangular numbers which are 7-almost primes.at n=33A076581
• Indices of primes in sequence defined by A(0) = 83, A(n) = 10*A(n-1) - 27 for n > 0.at n=7A101056
• Triangular numbers equal to the sum of a prime number with its index.at n=35A115886
• Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.at n=23A121898
• A difference triangle of Pascal-Sierpinski 5th level and the Pascal second derivative: a(n,k)= (4*n - 4*k + 1)a(n - 1, k - 1) + (4*k - 3)a(n - 1, k); p(x,n)=(Sum[10*n*(n - 1)*a(n, k)*x^(k - 1) - D[(x + 1)^(n + 2), {x, 2}]/(x + 1), {k, n}])/2.at n=10A155917
• a(n) = smaller member of n-th pair of distinct, positive, triangular numbers whose sum and difference are also triangular numbers.at n=11A185129
• Triangular numbers that are the product of two triangular numbers greater than 1.at n=28A188630
• Triangular numbers that are the product of three distinct triangular numbers greater than 1.at n=20A225440
• Triangular numbers that can be represented as a sum of two distinct triangular numbers, and as a product of two triangular numbers greater than 1.at n=12A295768
• Triangular numbers that can be represented as a product of two triangular numbers greater than 1, and as a product of three triangular numbers greater than 1.at n=9A295769
• Triangular numbers that are sandwiched between two squarefree semiprimes.at n=21A375384