56280

Appears in sequences

• Triangular numbers with sum of digits = 21.at n=33A068131
• Triangular numbers which are 7-almost primes.at n=20A076581
• Numbers that can be expressed as the difference of the squares of primes in exactly six distinct ways.at n=32A092002
• Indices of primes in sequence defined by A(0) = 89, A(n) = 10*A(n-1) - 41 for n > 0.at n=9A101069
• Triangular numbers for which the sum of the digits is an octagonal number.at n=36A117523
• Triangular numbers that are sandwiched between two semiprimes; or triangular numbers t such that t-1 and t+1 are both semiprime.at n=17A121898
• a(n) = 1*3*5 + 3*5*7 + 5*7*9 + ... (n terms).at n=12A196506
• Triangular numbers k whose divisors can be partitioned into three disjoint sets whose sums are all sigma(k)/3.at n=25A206025
• Triangular numbers T from A000217 such that (4*T+1)/13 is prime.at n=19A208294
• Triangular array read by rows. T(n,k) is the number of 2-colored labeled graphs on n nodes with exactly k connected components; n>=1, 1<=k<=n.at n=23A228892
• Numbers n such that {largest m such that 1, 2, ..., m divide n} is different from {largest m such that m! divides n^2}.at n=34A232099
• Number of (4+1) X (n+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=29A258557
• The first of two consecutive triangular numbers the sum of which is equal to the sum of two consecutive prime numbers.at n=22A298462
• Primorial deflation of the n-th colossally abundant number: the unique integer k such that A108951(k) = A004490(n).at n=30A342012
• Positive triangular numbers such that the two numbers before it and the two numbers after it are squarefree.at n=41A374503
• Triangular numbers that are sandwiched between two squarefree semiprimes.at n=15A375384
• Semiperimeter of the unique primitive Pythagorean triple whose inradius is the n-th prime and whose short leg is an odd number.at n=38A382070