18906

Appears in sequences

• Positive integers k such that k-th triangular number is palindromic.at n=23A008509
• Product of a prime and the following number.at n=32A036690
• a(n) = prime(n)*prime(n+1) - prime(n).at n=32A037166
• Index of the smallest n-digit palindromic triangular number, or 0 if no such number exists.at n=8A068642
• Index of the largest n-digit palindromic triangular number, or 0 if no such number exists.at n=8A068644
• Squarefree numbers k with largest prime factor = floor(sqrt(k)).at n=23A071311
• First differences of A084449.at n=39A084465
• Integers that are Rhonda numbers to base 12.at n=16A100971
• a(n) = number of conjugacy classes in PSL_3(prime(n)).at n=32A124679
• a(n) = (4*n+1)*(4*n+2) = (4*n+2)!/(4*n)!.at n=34A157870
• Number of different deltoids (including squares) whose vertices are on an n X n grid.at n=37A159944
• a(n) = 25*n^2 + 25*n + 6.at n=27A177059
• Binomial transform of A090426.at n=7A199297
• Number of (n+2) X 5 binary arrays avoiding patterns 001 and 110 in rows, columns and nw-to-se diagonals.at n=12A202442
• Triangle read by rows: T(n,k) appears in the transformation Sum_{k=0..n} (k+1)*x^k = Sum_{k=0..n} T(n,k)*(x+2k)^k.at n=29A253381
• G.f.: Sum_{n=-oo..+oo} ( x^n / (1 - x^(2*n)*(1+x)^(n+1)) )^2.at n=22A268656
• Maximum number of 6 sphinx tile shapes in a sphinx tiled hexagon of order n.at n=22A291582
• Numbers k such that the prime gap between the consecutive primes p1 < k^2 < p2 sets a new record.at n=21A350100
• Products of four distinct primes between sphenic numbers (products of 3 distinct primes).at n=7A351382
• Oblong numbers which are products of four distinct primes.at n=25A358988