27301

Appears in sequences

• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n-k+1), where k = [ n/2 ], s = (1, p(1), p(2), ...), t = (composite numbers).at n=41A025100
• a(n) is the sum of squares of the numbers in row n of array T given by A026148.at n=6A027335
• Row 7 of the array in A107735.at n=9A107731
• Those n for which A140259(n) = A002264(n+11).at n=20A140260
• Floor-Sqrt transform of large Schroder numbers (A006318).at n=14A192673
• Expansion of -(x*(1-sqrt((2*(1-sqrt(4*x^2+1)))/x+1)))/(1-sqrt(4*x^2+1)) - 1.at n=11A243814
• Consider a number x. Take the sum of its digits. Repeat the process deleting the first addendum and adding the previous sum. The sequence lists the numbers that after some iterations reach the arithmetic derivative of x.at n=27A269312
• Start with a square; at each stage add a square at each expandable vertex so that the ratio of the side of the squares at stage n+1 and at stage n is the golden ratio phi=0.618...; a(n) is the number of squares in a portion of the n-th stage (see below).at n=12A269963
• Semiprimes whose binary and ternary representations are prime when read in decimal.at n=32A279052
• Number of ways to choose a strict partition of each part of a strict partition of n.at n=25A279785
• Relative of Hofstadter Q-sequence: a(n) = max(0, n+27298) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.at n=3A283888
• Square array A(n,k), n >= 1, k >= 1, read by antidiagonals, where A(n,k) is the sum of distinct products Product_{j=1..k} b_j with 1 <= b_j<= n.at n=39A321163
• Centered pentagonal numbers which are squarefree semiprimes.at n=35A381043
• Centered pentagonal numbers which are semiprimes.at n=36A382132