20810

Appears in sequences

• a(0) = 1, a(n) = 18*n^2 + 2 for n>0.at n=34A010008
• Length of hypotenuse squared in right triangle formed by a prime spiral plotted in Cartesian coordinates.at n=26A048851
• Hypotenuses of special Pythagorean triples constructed from twin primes as follows: {u, w}={p,p+2}; side a=2p(p+2), side b=(p+2)^2-p^2 and the terms of sequence are values of c=a(n)=p^2+(p+2)^2=phi(a/2)+1+sigma(a/2)+1.at n=8A063533
• a(n) = prime(n+1)^2 + prime(n)^2.at n=25A069484
• Greatest number m such that the fractional part of (101/100)^A153669(n) <= 1/m.at n=10A153673
• G.f.: A(x) = exp( Sum_{n>=1} sigma(n)*A000204(n)*x^n/n ).at n=12A156234
• Number of partitions of n such that the number of parts and the greatest part are not coprime.at n=41A200792
• T(n,k)=Number of idempotent n X n 0..k matrices of rank n-2.at n=19A224118
• Number of idempotent 5X5 0..n matrices of rank 3.at n=1A224119
• Number of integer partitions of prime(n) into a prime number of prime parts.at n=27A316154
• Triangle T(n,k) read by rows: T(n,k) = the number of ways of seating n people around a table for the second time so that k pairs are maintained. Reflected and rotated sequences are counted as one.at n=59A326411
• a(n) is twice the coefficient of 1 in the fundamental unit of Q(sqrt(A000037(n))) where A000037 lists the nonsquare numbers (Version 2).at n=76A346419