18095

Appears in sequences

• Lucas-Carmichael numbers: squarefree composite numbers k such that p | k => p+1 | k+1.at n=9A006972
• Sum of 1-fibits in Zeckendorf-expansion A014417(p) summed for all primes p in range [Fib(n+1),Fib(n+2)[ (where Fib = A000045).at n=22A095353
• A triangular sequence from a Beraha type recursive polynomial using 5 X 5 centered tridiagonal matrices with chromatic polynomial central roots to its characteristic polynomial.at n=44A123969
• Pentagonal numbers that are the sum of a nonzero pentagonal number and a nonzero square in at least one way.at n=39A134938
• Numbers expressible in more than one way as 6^x-y^2.at n=15A134989
• Least pentagonal number P(m) > P(n) such that P(m)+P(n) is again a pentagonal number, 0 if no such m exists.at n=39A136114
• Pentagonal numbers (A000326) which are the sum of 2 other positive pentagonal numbers.at n=24A136117
• Numbers k such that k and k+1 have 4 distinct prime factors.at n=20A140078
• Lucas-Carmichael numbers with 4 prime factors.at n=1A216926
• Least Lucas-Carmichael number divisible by the n-th prime.at n=13A253597
• a(n) = least Lucas-Carmichael number which is divisible by b(n), where {b(n)} (A255602) is the list of all numbers which could be a divisor of a Lucas-Carmichael number.at n=17A253598
• Total number of congruence subgroups of PSL(2,Z) of genus n.at n=12A258691
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 531", based on the 5-celled von Neumann neighborhood.at n=26A272752
• Number of 2 X 2 matrices with all elements in {0,...,n} and prime determinant.at n=22A281315
• Number of set partitions of [n] such that all absolute differences between least elements of consecutive blocks and between consecutive elements within the blocks are not larger than six.at n=9A287585
• Numbers k such that k!6 - 36 is prime, where k!6 is the sextuple factorial number (A085158).at n=21A289700
• Generalized Lucas-Carmichael numbers for D=9697.at n=39A290560
• Positive integers m such that m, m + 1 and m + 2 are a sum of a positive square and a positive cube.at n=41A295787
• a(n) = (A001359(n+1)^2 - 1)/24, where A001359 = lesser of twin primes; or: pentagonal numbers (A000326) whose indices are twin ranks (A002822).at n=28A308344
• Numbers k such that k and k+1 each have at least 4 distinct prime factors.at n=20A321504