21970

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 61.at n=34A020400
• Numbers k that divide 9^k + 7^k.at n=19A045605
• Numbers of the form (10^i)*(13^j), with i, j >= 0.at n=13A108761
• Triangle of coefficients in expansion of (1+13x)^n.at n=18A123187
• Triangle read by rows: T(i,j) is the number of i-permutations of 14 objects a,b,c,d,e,f,g,h,i,j,k,l,m,n, with repetition allowed, containing j a's.at n=17A133371
• Numbers k with equal remainders of (product of divisors of k) mod (sum of divisors of k) and (product of proper divisors of k) mod (sum of proper divisors of k).at n=38A192035
• Number of n X 2 (-1,0,1) arrays of determinants of 2 X 2 subblocks of some (n+1) X 3 binary array with rows and columns of the latter in lexicographically nondecreasing order.at n=14A226866
• Number of compositions of n avoiding three consecutive parts in arithmetic progression.at n=17A238423
• a(n) = 10*n^3.at n=13A244729
• Numbers whose squares became cubes if some digit is prepended, inserted or appended.at n=23A248127
• Numbers m such that sigma(sigma(m))/m is a square.at n=21A318084
• Primitive terms of A370348.at n=37A370406
• Nonsquarefree numbers k such that A003415(k) divides A276086(k), where A003415 is the arithmetic derivative, and A276086 is the primorial base exp-function.at n=36A371085
• Consider primitive pairs of integers (b, c) with b > 0 such that x^5 + b*x + c = 0 is irreducible and solvable by radicals: sequence gives values of b.at n=26A371553
• Consider primitive pairs of integers (b, c) with b > 0 such that x^5 + b*x + c = 0 is irreducible and solvable by radicals: sequence gives values of b.at n=27A371553
• Numbers k such that there are least five primitive Heron triangles having the same area and perimeter k.at n=13A385819