212521

Appears in sequences

• a(n) = (12*n + 5)^2.at n=38A017582
• Squares-of-primes in which no two adjacent digits have the same parity.at n=17A030146
• Squares in which parity of digits alternates.at n=42A030152
• Odd squares in which parity of digits alternates.at n=26A030156
• Smallest nontrivial extension of n-th palindrome which is a square.at n=29A030676
• Squares composed of digits {1,2,5}.at n=8A031151
• Squares resulting from procedure described in A048383.at n=19A048384
• a(n) = n*(n+1)*(n+2)*(n+3)+1 = (n^2 + 3*n + 1)^2.at n=20A062938
• Squares with property that digits alternate in parity individually as well as in concatenation with previous terms.at n=18A068888
• Perfect powers using only prime digits and 1.at n=20A083806
• a(n) = x^2 = A090116(n)^2 is the least square that is "surrounded" by two closest primes, by prevprime(x^2) and nextprime(x^2) whose difference nextprime - prevprime = 2n.at n=24A090117
• Squares of A006450: a(n) = prime(prime(n))^2.at n=23A092769
• Unsigned member r=-20 of the family of Chebyshev sequences S_r(n) defined in A092184.at n=5A099278
• Squares of lesser of twin primes.at n=23A108570
• Numbers k such that sigma(k) - phi(k) is a brilliant number (A078972).at n=30A115917
• Numbers n such that max(tau(n),tau(n+1),tau(n+2))- min(tau(n),tau(n+1),tau(n+2)) = 1.at n=29A173149
• Prime powers p^k with even exponents k > 0 such that (1 + p^k)/2 is prime.at n=25A192618
• Composite numbers with both 10 and -10 as primitive root.at n=20A218766
• The smaller of a pair of successive powerful numbers (A001694) without any prime number between them.at n=28A240591
• Squares s such that s + 1234567890 is prime.at n=18A241538