20025

Appears in sequences

• Convolution of natural numbers with Beatty sequence for tau^2 A001950.at n=34A023542
• Convolution of the lower and upper Wythoff sequences (A000201 and A001950).at n=29A023664
• Numbers n such that 29^n + 2 is prime.at n=11A087886
• Numbers n such that sigma(sigma(phi(n))) = sigma(sigma(n)).at n=25A172466
• G.f.: Sum_{n>=0} n! * x^(n*(n+1)/2) / Product_{k=1..n} (1 - k*x^k).at n=20A204858
• Numbers that match polynomials over {0,1} that have a factor containing -3 as a coefficient; see Comments.at n=28A208182
• Number of (n+2)X(1+2) 0..4 arrays with every 3X3 subblock row and column sum prime and every diagonal and antidiagonal sum nonprime.at n=2A251878
• Number of (n+2)X(3+2) 0..4 arrays with every 3X3 subblock row and column sum prime and every diagonal and antidiagonal sum nonprime.at n=0A251880
• T(n,k)=Number of (n+2)X(k+2) 0..4 arrays with every 3X3 subblock row and column sum prime and every diagonal and antidiagonal sum nonprime.at n=3A251885
• T(n,k)=Number of (n+2)X(k+2) 0..4 arrays with every 3X3 subblock row and column sum prime and every diagonal and antidiagonal sum nonprime.at n=5A251885
• a(0)=0, a(1)=1, a(n) = min{4 a(k) + (4^(n-k)-1)/3, k=0..(n-1)} for n>=2.at n=24A259665
• Triangle read by rows: T(n,k) (n>=0, k>=0) is the number of permutations of n with k alignments.at n=50A263775
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 910", based on the 5-celled von Neumann neighborhood.at n=40A273764
• Numbers k such that (38*10^k + 187)/9 is prime.at n=16A295631
• Numbers k in A228058 such that also A001065(k) is in A228058.at n=27A325380
• Triangle read by rows: T(n,k) is the number of achiral colorings of the edges of a regular n-D orthotope (or ridges of a regular n-D orthoplex) using exactly k colors. Row n has n*2^(n-1) columns.at n=9A338145
• Triangle read by rows: T(n,k) is the number of achiral colorings of the edges of a regular n-D orthoplex (or ridges of a regular n-D orthotope) using exactly k colors. Row 1 has 1 column; row n>1 has 2*n*(n-1) columns.at n=9A338149
• Index of first occurrence of n in A348179, or -1 if n never appears.at n=25A349423
• Numbers k divisible by A004719(k), excluding trivial cases.at n=36A386501
• Terms k of A228058 for which A048146(k)+A162296(k) >= 2*k, where A048146 is the sum of non-unitary divisors, and A162296 is the sum of divisors that have a square factor.at n=27A389219