64980

Appears in sequences

• Triangular numbers which are 7-almost primes.at n=22A076581
• Smallest triangular number having n^2 as divisor.at n=18A080983
• Numbers k such that the sets of prime factors (ignoring multiplicity) of A000203(k) = sigma(k) and of A001157(k) = sigma_2(k) are identical.at n=8A081380
• a(n) = n^2 * (n^2 - 1)/2.at n=18A083374
• Triangular numbers > 0 with a prime signature that has not occurred earlier.at n=36A085076
• Triangular numbers all of whose digits are nonprimes.at n=31A111484
• Triangular numbers for which the sum of the digits is a cube.at n=22A117803
• Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.at n=18A121898
• Column 3 of triangle A123610.at n=17A123613
• a(n) = ((n-th prime)^4-(n-th prime)^2)/2.at n=7A138418
• Number of n X 4 1..3 arrays containing at least one of each value, and all equal values connected.at n=3A166767
• Let T(n) = n(n+1)/2 be the n-th triangular number (A000217); a(n) = T(8T(n)).at n=9A185096
• Triangular numbers k whose divisors can be partitioned into three disjoint sets whose sums are all sigma(k)/3.at n=28A206025
• Number of 2 X 2 matrices with all terms in {0,1,...,n} and odd trace.at n=18A210379
• Triangular numbers which are an average of four consecutive primes.at n=31A226196
• Positive integers, c, such that there are more than two solutions to the equation a^2 + b^3 = c^4, with a, b > 0.at n=38A242381
• Triangular numbers that are the product of a triangular number and a square number (both greater than 1).at n=8A253650
• Triangular numbers that are the product of a triangular number and an oblong number.at n=24A253652
• Triangular numbers that are the product of a square number and a prime number.at n=22A253653
• Expansion of Product_{k>=1} 1/(1 - k*x^k)^(k^2).at n=9A285241