28980

Appears in sequences

• a(n) = 1 + L(n) + F(2*n-1) with {L(n)}_{n>=0} the Lucas numbers (A000032) and F(2*n-1)_{n>=0} the bisected Fibonacci numbers (A001519).at n=12A005522
• Numbers k such that the number of steps to reach 1 in '3x+1' problem equals tau(k), the number of divisors of k.at n=35A070980
• Lexicographically least sequence such that a(n) is a positive multiple of the n-th composite number and the arithmetic mean of the first n terms is an integer.at n=48A095211
• Triangle read by rows: T(n,h)/(n-1), where T is the array in A101819.at n=23A101820
• Denominators of the greedy Egyptian partial sums for L(3, chi3), where L(s, chi3) is the Dirichlet L-function for the non-principal character modulo 3.at n=4A129665
• 12 times hexagonal numbers: 12*n*(2*n-1).at n=35A143698
• a(n) = 1000*n - 20.at n=28A157515
• Record differences for n^2 - phi(n)*sigma(n).at n=34A164876
• Smallest number which is an unordered sum of two odd abundant numbers in exactly n ways.at n=22A187743
• Numbers with prime factorization pqrs^2t^2.at n=7A189989
• Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,2,1,3,4 for x=0,1,2,3,4.at n=18A196132
• Numbers that are products of two triangular numbers in more than one way.at n=47A264961
• Least m>0 for which m + n^2 is a square and m + triangular(n) is a triangular number (A000217).at n=36A267140
• Numbers k such that 1/phi(x) + 1/phi(y) = 1/phi(k), for some x + y = k and phi(k) is the Euler totient function of k.at n=36A279621
• Number of cyclic compositions (necklaces of positive integers) summing to n that have only one part or whose consecutive parts (including the last with first) are indivisible.at n=35A318729
• a(n) = Sum_{k=0..n} k^(2*n) * Stirling1(n,k).at n=4A351183
• Expansion of g.f. A(x) satisfying 4*x = Sum_{n=-oo..+oo} x^(n*(3*n+1)/2) * (A(x)^(3*n) - 1/A(x)^(3*n+1)).at n=5A361554
• Numbers k such that A383543(k) > A383543(m) for all m < k.at n=11A383544
• Triangle read by rows: T(n,k) is the number of noncrossing path sets on n nodes with k paths and isolated vertices allowed, 0 <= k <= n.at n=61A390909