21397

Properties

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 32.at n=2A031620
• Euclid-Mullin sequence (A000945) with initial value a(1)=19 instead of a(1)=2.at n=24A051312
• Smallest prime in n-th shell of prime spiral.at n=25A053998
• First term of weak prime sextet: p(m+1)-p(m) < p(m+2)-p(m+1) < p(m+3)-p(m+2) < p(m+4)-p(m+3) < p(m+5)-p(m+4).at n=6A054828
• Primes p for which the period of reciprocal 1/p is (p-1)/12.at n=25A056217
• Primes congruent to 39 mod 59.at n=40A142766
• Expansion of x/((1 - x - x^4)*(1 - x)^5).at n=15A145134
• Smaller member of a pair (p,q) of cousin primes such that p and q are in different centuries.at n=20A160440
• Numbers n such that n contains exactly 5 digits, all distinct, and n^2 contains exactly 9 distinct digits.at n=16A204691
• Let A = A025584. a(n) is the smallest A(m) such that the interval (A(m)*n, A(m+1)*n) contains no primes from A.at n=22A207820
• Records in A096335 (values).at n=38A221181
• Primes formed from concatenation of PrimePi(n) and prime(n).at n=27A236551
• Primes of the form n^2 + 81.at n=17A256775
• Primes p such that both p and p^2 are distinct-digit numbers.at n=48A259187
• Least number x such that x^n has n digits equal to k. Case k = 8.at n=17A285455
• Prime time primes on 6-digit clocks, second definition: primes of the form HMMSS where H, MM, SS are primes, H < 24, MM and SS < 60.at n=34A295013
• Number of Motzkin paths of length n with all ascents ending at odd heights.at n=14A299271
• Numbers that are the sum of seven fourth powers in six or more ways.at n=29A345572
• Numbers that are the sum of seven fourth powers in exactly six ways.at n=21A345828
• First of three consecutive primes whose concatenations, both forward and backward, are primes.at n=40A384953