relations on n points: A001173 * (unlabeled), A000595 * (labeled)
relations, antisymmetric transitive: A091566
relations, antisymmetric: A001174 *
Relations, connected, A002501 , A002502
Relations, dissimilarity, A006541
Relations, reflexive, A000666 , A000250
relations, self-converse: A002500 *
relations, symmetric reflexive: A000250 *
relations, symmetric: A000666 *, A070166
relations, transitive: A006905 * A091073 *
Relations, ultradissimilarity, A005121
Relations, vacuously transitive, A003041
relations, without symmetry: A030242 *
relations: see also A000665 , A000957 , A000663 , A000662 , A001377 , A001374 , A001376 , A001375
relatively prime pairs of numbers: see pairs of relatively prime numbers
relatively prime triples of numbers: see triples of relatively prime numbers
remove 2's from n: A000265
remove squares!: A002734
rencontres numbers, triangle of: A008290 *
rencontres numbers: A000166 *
rencontres numbers: see also A000240 , A000387
Rencontres numbers:: A000166 *, A000387 , A000449 , A000475
repdigit (repeated digit) numbers: A010785 *
repeating substrings: see doubling substrings
repfigit or Keith numbers: A007629 *, A06576*
Representation degeneracies:: A005290 , A005292 , A005291 , A005297 , A005299 , A005293 , A005304 , A005294 , A005300 , A005298 , A005303 , A005305 , A005306 , A005295 , A005296 , A005301 , A005302
Representations as sums of Fibonacci numbers, A000119 , A000121 , A006133 , A006132
Representations as sums of increasing powers, A003315
Representations as sums of Lucas numbers, A003263
Representations as sums of squares, A006892 , A002291 , A002611 , A002470 , A002290 , A002610 , A002614 , A002288 , A002612 , A002607 , A002615 , A002292 , A002609 , A002608 , A002613
Representations as sums of triangular numbers, A006894 , A006893
Representations of 0, A000980
Representations of 1, A002967
Representations of symmetric group, A000701
repunit primes: see primes, repunit
repunits: A002275 *, A003020