45451

Appears in sequences

• Strong pseudoprimes to base 36.at n=37A020262
• Strong pseudoprimes to base 44.at n=29A020270
• Terms of A073872 that do not change their position in the rearrangement; i.e., values of A073872(n) which equal n(n+1)/2.at n=22A073873
• Sort the digits of these triangular numbers into descending order and drop zeros to get primes.at n=37A082923
• Triangular numbers whose sum of aliquot divisors is a prime number.at n=23A083676
• Numbers k such that k*(k+5) gives the concatenation of two numbers m and m-4.at n=9A116261
• Hexagonal numbers with prime indices.at n=35A117961
• Triangular numbers composed of digits {1,4,5}.at n=6A119123
• Hexagonal numbers (A000384) which are sum of 2 other hexagonal numbers > 0.at n=33A133215
• A triangle sequence of the form:t(n,m]=If[m == 0 || m == n, 1, Binomial[Eulerian[n + 1, m], If[Floor[n/2] < m, n - m, m]]].at n=17A174036
• A triangle sequence of the form:t(n,m]=If[m == 0 || m == n, 1, Binomial[Eulerian[n + 1, m], If[Floor[n/2] < m, n - m, m]]].at n=18A174036
• a(n) = m*(m+1)/2, where m = floor(n^(3/2)).at n=44A185541
• Triangular numbers composed of only digits with line segments or both line segments and curves {1, 2, 4, 5, 7}.at n=21A247021
• a(n) = A000217(A000217(n)+1).at n=24A267707
• Numbers k such that (73*10^k - 91)/9 is prime.at n=21A294488
• a(n) = n*((4*n + 1)*(7*n - 4) + 15*n*(-1)^n)/48.at n=42A302766
• Terms of A324315 (squarefree integers m > 1 such that if prime p divides m, then the sum of the base p digits of m is at least p) that are also hexagonal numbers (A000384) with index equal to their largest prime factor.at n=9A324319
• NSW pseudoprimes: odd composite numbers k such that A002315((k-1)/2) == 1 (mod k).at n=31A330276
• Odd composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 5 (mod m), where U(m) and V(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=5 and b=-1, respectively.at n=33A337628
• Triangular numbers that in base 2 have the same number of 0's and 1's.at n=31A345348