19998

Appears in sequences

• Number of aperiodic necklaces of n beads of 10 colors.at n=4A032165
• 4-white numbers: partition digits of n^4 into blocks of 4 starting at right; sum of these 4-digit numbers equals n.at n=11A037044
• 1/3-Smith numbers.at n=1A050225
• Number of nonzero palindromes less than 10^n.at n=7A050250
• a(n)=phi(n^2+1)/n if (n^2+1) is composite and phi(n^2+1)==0 (mod n).at n=32A067926
• Integers n such that n = A067030(j) for some j and A067286(j) < A067034(j).at n=21A068798
• Smallest even number with digit sum n.at n=35A069532
• Numbers n for which there is a unique k such that n = k + reverse(k).at n=44A072427
• Numbers k such that 4*k-1 is the digit reversal of k-1.at n=3A083812
• a(n) = 2*(10^n - 1).at n=4A086573
• Permanent of (0,1)-matrix of size n X (n+d) with d=5 and n-1 zeros not on a line.at n=4A090015
• Triangular Kaprekar-like numbers: numbers k such that the base-10 representation of T(k) = k*(k+1)/2 is the concatenation of two numbers x and y such that x + y = k.at n=37A110939
• Number of partitions of n such that the largest part and the smallest part are relatively prime.at n=36A117087
• Where records occur in A119451.at n=18A119453
• Order of the following permutation on 3n+1 symbols. Write the 3n+1 symbols horizontally into a 3-column grid and read them off vertically, i.e., column after column.at n=47A119980
• Integer squares y from the smallest solutions of y^2 = x*(a^N - x)*(b^N + x) (elliptic line, Weierstrass equation) with a and b legs in primitive Pythagorean triangles and N = 2. Sequence ordered in increasing values of leg a.at n=16A120210
• A Moessner triangle using (1, 2, 1, 2, 1, 2, ...).at n=29A125751
• 3 times 9-gonal (or nonagonal) numbers: a(n) = 3*n*(7*n-5)/2.at n=44A152759
• Twice repdigit numbers.at n=36A152966
• Numbers n, not relatively prime to 10, such that the decimal form of the period of 1/n is prime.at n=56A179192