20131

Appears in sequences

• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (composite numbers), t = (odd natural numbers).at n=39A024590
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (odd natural numbers), t = A000201 (lower Wythoff sequence).at n=41A024599
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (composite numbers), t = (odd natural numbers).at n=38A025104
• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (odd natural numbers), t = A000201 (lower Wythoff sequence).at n=40A025113
• a(n) = dot_product(1,2,...,n)*(6,7,...,n,1,2,3,4,5).at n=35A026046
• Numbers whose set of base-11 digits is {1,4}.at n=40A032823
• a(n) = (2*n - 1)*(7*n^2 - 7*n + 6)/6.at n=20A063490
• a(n) = (n^3 + 18*n^2 + 17*n + 6)/6.at n=44A143058
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (0, 1, 0), (1, 0, 0), (1, 1, -1), (1, 1, 1)}.at n=7A151153
• a(n) is the largest number k such that there is no pair p+q = 2*k of two non-consecutive primes p < q with p-2*n,p or p,p+2*n consecutive primes and q-2*n,q or q,q+2*n consecutive primes.at n=3A159812
• Number of tilings of a 20 X n rectangle using 2n decominoes of shape I.at n=29A250667
• Expansion of (1/(1 - x)) * Sum_{k>=0} x^(k*(2*k+1)) / Product_{j=1..2*k} (1 - x^j).at n=52A318155
• Expansion of (1/(1 - x)) * Sum_{k>=1} x^(k*(2*k-1)) / Product_{j=1..2*k-1} (1 - x^j).at n=52A318156
• Smallest k > 1 such that k^n - 1 is the product of n distinct primes.at n=12A359070
• Numbers k that are the representation of primes in base 4 and in base 5.at n=23A359840